Growing Flannel Flowers all Year Round
RIRDC Publication No. 10/065
Growing Flannel Flowers all
Year Round
By Dr Ross Worrall and Len Tesoriero
May 2010
RIRDC Publication No 10/065
RIRDC Project No. PRJ-000498
© 2010 Rural Industries Research and Development Corporation.
All rights reserved.
ISBN 978-1-74254-038-2
ISSN 1440-6845
Growing Flannel Flowers all Year Round
Publication No. 10/065
Project No.PRJ-000498
The information contained in this publication is intended for general use to assist public knowledge and discussion
and to help improve the development of sustainable regions. You must not rely on any information contained in
this publication without taking specialist advice relevant to your particular circumstances.
While reasonable care has been taken in preparing this publication to ensure that information is true and correct,
the Commonwealth of Australia gives no assurance as to the accuracy of any information in this publication.
The Commonwealth of Australia, the Rural Industries Research and Development Corporation (RIRDC), the
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The Commonwealth of Australia does not necessarily endorse the views in this publication.
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Researcher Contact Details
Dr Ross Worrall
Industry and Investment NSW
LB 26 Gosford NSW 2250
Phone
Fax:
Email:
(02) 4348 1900
(02) 4349 1910
[email protected]
In submitting this report, the researcher has agreed to RIRDC publishing this material in its edited form.
RIRDC Contact Details
Rural Industries Research and Development Corporation
Level 2, 15 National Circuit
BARTON ACT 2600
PO Box 4776
KINGSTON ACT 2604
Phone:
Fax:
Email:
Web:
02 6271 4100
02 6271 4199
[email protected]
http://www.rirdc.gov.au
Electronically published by RIRDC in May 2010
Print-on-demand by Union Offset Printing, Canberra at www.rirdc.gov.au
or phone 1300 634 313
ii
Foreword
There is a well-established domestic and export market for cut flannel flowers (Actinotus helianthi)
with out-of-season flowers commanding a significant premium. Demand already exceeds supply,
which will be exacerbated in the future with proposed actions to severely reduce bush picking. To
date, Actinotus sp. has proven unreliable in cultivation as it is difficult to propagate and has a short
flowering season limited to spring and early summer. In response, the Flannel Flower Forum has
identified the major constraints limiting cultivation – in particular the lack of suitable varieties,
cultural information, propagation and the effect of root diseases. Overcoming these production
constraints will provide business and employment opportunities for regional Australia.
This report details the development of a high yielding year-round flowering clone of flannel flower in
terms of propagation protocols, cultural requirements and post-harvest recommendations. A new
greenhouse industry of Australian native cut flower production has already been instigated as a result
of providing this information to industry participants throughout the course of this project.
The Rural Industries Research and Development Corporation (RIRDC) invests in new and emerging
industries on behalf of government and industry stakeholders. New industries provide opportunities to
be captured by rural producers and investors. They also provide avenues for farmers facing adjustment
pressure to diversify and manage change. The establishment of new industries contributes to
community resilience and regional development. Increasingly, new industries are also contributing to a
distinctive regional character in rural Australia.
The importance of this report is that it provides basic information for the development of a new
industry based on protected cultivation.
This project was funded from RIRDC Funds which are provided by the Australian Government,
Industry and Investment NSW and growers.
This report, an addition to RIRDC’s diverse range of over 2000 research publications, forms part of
our Wildflowers and Native Plants R&D program, which aims to improve the profitability,
productivity and sustainability of the Australian wildflower and native plant industry.
Most of RIRDC’s publications are available for viewing, free downloading or purchasing online at
www.rirdc.gov.au. Purchases can also be made by phoning 1300 634 313.
Peter O’Brien
Managing Director
Rural Industries Research and Development Corporation
iii
Acknowledgments
The authors wish to thank cooperating researchers and extension personnel whose input made this
project possible, especially Dr Lindsay Campbell, University of Sydney; Dr Cathy Offord, Royal
Botanic Gardens (Mount Annan); Lotte von Richter, Royal Botanic Gardens (Mount Annan);
Dr Rod King (CSIRO Canberra); Bettina Gollnow (NSW DPI); and Greig Ireland (I&I NSW).
Thanks also go to Pauline Cain, Fiona Lidbetter and Vicky Worrall who provided technical assistance
and helped make things happen.
Assistance in statistical analysis was provided by Lorraine Sphor and Anne Harris of the Gosford
Horticultural Research Institute.
Thank you also to the Rural Industries Research and Development Corporation; the Royal Botanic
Gardens; and Domain Trust (Sydney) for financial support and also to the many employees of I&I
NSW who participated in this project.
The contribution of commercial co-operators who provided valuable information on the cultivation of
Actinotus helianthi for this project is acknowledged:
Alexander
Paul
Terry
Geoff
Stephen
Harry
Pelser
Dalley
Flanagan
Hammond
Holden
Kibbler
David
Chris
Alex
Craig
Brian
Rick
& Mary
Brian & Pat
Shaun
Tony
Peter
Matheson
Miller
Orgill
Scott
Shannon
Smith
Lomond
Sundin
Ward
Waugh
Zulpo
Something Wild Flower Farm
Mountain Nursery
Flora Inspirations
Glenona Gardens
Native Flower Growers' Association (Mid North Coast)
Inc.
Native Flower Growers Co-op
Eastwood Nurseries
Shoreowl Pty Ltd
East Coast Wildflowers
Shannon Roses
Marick Nursery
Sandy Manor Flowers
Weatherby Downs Pty Ltd
Zfarm
iv
Abbreviations
AFP
Ag
ANOVA
B
Ca
CAN
Cl
Co
Cu
dS m-1
EC
Fe
GA
GHI
HQS
IBDU
I&I NSW
K
lsd
m
M
Mg
Mn
Mo
mS/m
N
Na
NaCl
P
PDA
ppm
PT
R2
SME
SPE
STS
µ
Zn
Air Filled Porosity
silver
analysis of variance
boron
calcium
coated ammonium nitrate
chlorine
cobalt
copper
deciSiemens per metre
electrical conductivity
iron
gibberellic acid
Gosford Horticultural Research Institute
8-hydroxy quinoline sulphate
isobutylidene diurea
Industry and Investment NSW
potassium
least significant difference
milli
molar
magnesium
manganese
molybdenum
milliSiemens per metre
nitrogen
sodium
sodium chloride (common salt)
phosphorus
potato dextrose agar
parts per million
Pour Through technique
correlation coefficient
Saturated Medium Extract
Saturated Paste Extract method
silver thiosulphate
micro
zinc
v
Contents
Foreword .............................................................................................................................................. iii
Acknowledgments.................................................................................................................................iv
Abbreviations .........................................................................................................................................v
Tables ........................................................................................................................................... vii
Figures ......................................................................................................................................... viii
Executive Summary .............................................................................................................................ix
1.
Introduction ...................................................................................................................................1
2.
Flannel Flower Diseases ................................................................................................................3
2.1 .. Introduction .............................................................................................................................3
2.2 .. Survey of A. helianthi diseases................................................................................................4
2.3 .. Trials with potential pathogens ...............................................................................................6
3.
Plant Nutrition
15
3.1 .. Response of flannel flowers to fertilisers ..............................................................................15
3.2 .. The effect of NaCl on the growth of A. helianthi ..................................................................19
4.
Cluster Roots................................................................................................................................24
4.1. . Introduction ...........................................................................................................................24
4.2 .. Materials and methods...........................................................................................................24
4.3 .. Results and discussion ...........................................................................................................25
5.
The Effect of Growing Media on the Growth of Actinotus and Other Species ......................27
5.1 .. Introduction ...........................................................................................................................27
5.2 .. The effect of growing media on growth of Actinotus and tomato .........................................28
5.3 .. The effect of growing medium on flower production of a range of species..........................30
6.
Use of Gibberellic Acid (GA) to Increase Flower Stem Length ..............................................32
6.1 .. Introduction ...........................................................................................................................32
6.2 .. Materials and methods...........................................................................................................32
6.3 .. Results and discussion ...........................................................................................................32
7.
Propagation of Actinotus and Varietal Performance ...............................................................35
7.1 .. Seedling material ...................................................................................................................35
7.2 .. Other flannel flower hybrids .................................................................................................36
8.
Post-Harvest Characteristics of Actinotus .................................................................................37
8.1 .. Introduction ...........................................................................................................................37
8.2 .. Materials and methods...........................................................................................................38
8.3 .. Results and discussion ...........................................................................................................39
8.4 .. Conclusions ...........................................................................................................................39
9.
Discussion and Key Findings ......................................................................................................40
10. Recommendations .......................................................................................................................41
Appendix 1 ...........................................................................................................................................42
Growing flannel flowers for the cut flower market – A guide for commercial growers ...............42
References ............................................................................................................................................43
vi
Tables
Table 2.1
Table 2.2
Table 2.3
Table 2.4
Table 2.5
Table 2.6
Table 2.7
Table 3.1
Table 3.2
Table 5.1
Table 5.2
Table 5.3
Table 6.1
Table 6.2
Potential pathogens identified by the Plant Disease Health Service (I&I NSW) ...............5
Potential pathogen, accession number and source plant .....................................................6
Analysis of variance for weight and root score ..................................................................8
The effect of pathogen and disease on dry weight and root score ......................................8
Pathogens and carrier used in experiment 2.3.2 .................................................................9
Predicted dry weight means ..............................................................................................10
List of potential pathogens in experiment 2.3.3 ................................................................11
Leaf nutrient levels for healthy leaves ..............................................................................16
Conductivity readings for the salinity tolerance of plants grown in organic-based
media (Bunt 1976) ............................................................................................................19
Air Filled Porosity of growing media and the effect of media on the dry weight of
Actinotus and Lycopersicon esculentum ...........................................................................29
Nitrogen draw down of organic components ....................................................................29
Air Filled Porosity of growing media and the effect of media on the number of
flowers of different flower species/varieties .....................................................................31
Statistical analysis of stem length .....................................................................................32
Statistical analysis for number of flowers harvested. .......................................................34
vii
Figures
Figure 1.1
Commercial production of Actinotus following this project ...............................................1
Figure 1.2 Greenhouse purpose-built for the production of Actinotus flowers ....................................2
Figure 1.3 Actinotus being grown in pre-existing greenhouse .............................................................2
Figure 2.1 General view of experiment 2.3 ........................................................................................11
Figure 2.2 The effect of root disease on Actinotus ............................................................................12
Figure 2.3 Root systems showing the effect of diseases ....................................................................13
Figure 2.4 Dry weight versus root score. As root damage increased, growth rate was reduced ........13
Figure 3.1 The effect of applied rate of superphosphate on tissue P level. Fitted equation and its
correlation coefficient are shown on the graph. ................................................................17
Figure 3.2 The effect of tissue P on dry weight. The fitted equation and its correlation coefficient
(R2) are shown on the graph .............................................................................................17
Figure 3.3 The effect of CAN rate on leaf tissue N. Fitted equation and its correlation coefficient
(R2) are shown on the graph. ............................................................................................18
Figure 3.4 EC of the growing medium compared to concentration of NaCl in irrigation water ........20
Figure 3.5 The effect of NaCl on the growth of plants ......................................................................21
Figure 3.6 The effect of NaCl on the survival of Actinotus ...............................................................22
Figure 3.7 Salinity reduces the growth rate of Actinotus ...................................................................22
Figure 3.8 Salinity reduces the growth of Tagetes patula..................................................................22
Figure 3.9 Symptoms of high salinity (leaf burn) on flannel flower ..................................................23
Figure 3.10 The effect on flannel flower plants exposed to a high level of salinity ............................23
Figure 4.1 Dwarf Actinotus helianthi growing in its natural habitat ..................................................25
Figure 4.2 Cluster roots on Actinotus helianthi .................................................................................26
Figure 5.1 General view of initial selection pilot trials ......................................................................27
Figure 6.1 The effect of GA on plant height. .....................................................................................33
Figure 6.2 The effect of GA on stem length ......................................................................................33
Figure 7.1 High germination rate of Actinotus seed in trays has enabled commercial
production from seed ........................................................................................................35
Figure 7.2 Following germination, seed is transplanted to seedling trays that are then
transplanted into growing containers ................................................................................35
Figure 7.3 Tissue culture of clone C1 in the laboratory .....................................................................36
Figure 7.4 Commercial production of C1 in a greenhouse ................................................................36
Figure 7.5 Few flowers were produced by some of the selected clones of Actinotus ........................36
Figure 8.1 Normal post-harvest handling practices for Actinotus grown in protected cultivation .....37
Figure 8.2 Normal harvest stage for Actinotus cv C1 inflorescences.................................................38
Figure 8.3 The effect of preservative solutions on vase life ..............................................................39
viii
Executive Summary
What the report is about and who it is targeted at?
The aim of this project was to develop Actinotus helianthi as a cut flower crop under protected
cultivation. Previously this plant was bush harvested with limited field cultivation. Improving growing
conditions can result in better quality flowers and extend seasonal availability. This project has the
potential to expand the Australian export market, enhancing the profitability of Australian native cut
flower and foliage production. This report is targeted at current and potential wildflower growers.
Background
The domestic and export market for flannel flowers is currently estimated at $2 million per annum
with demand exceeding supply. Flannel flower is recognised as a ‘difficult’ crop of high risk but it
also has the ability to provide high returns. Overcoming production constraints could potentially
increase flannel flower exports by a factor of 5 to 10. Cultivated flowers have a good vase life and
transport well. Currently the net return (farm gate) is about 50 cents for a 50 cm stem of flowers sold
to Japan with out-of-season flowers commanding a significant premium.
The key impediments facing the cultivation of flannel flower crops were reviewed in a one-day
workshop (Jones and Worrall 2001). The following problems were identified: (1) root diseases and
their interaction with growing medium aeration, (2) availability of elite clonal material, (3)
propagation and (4) lack of post-harvest handling information (von Richter and Offord, 1997, 2000;
Carson, 2000; Jones and Worrall, 2001; Faragher et al. 2002). A systems approach is required to
solve these critical problems to make cultivation commercially viable.
Preliminary trials by the Department of Industry and Investment New South Wales (I&I NSW)
demonstrated the feasibility of producing the plants under protected cultivation. A clone developed by
I&I NSW performed well in initial trials and produced exceptionally high yields all year round – a
first for flannel flowers. However, development was needed before commercial release, especially in
relation to propagation, growing medium, effect of growth regulators on stem length, and disease
control.
Aims/objectives
This project aimed to overcome important impediments to the profitable cultivation of flannel flowers
(Actinotus helianthi) by producing a package of new varieties, cultural information and post-harvest
recommendations. This would enable flannel flowers to be grown reliably in protected cultivation.
This model production system for flannel flower in protected cultivation could also be used to assess
other potential crops.
Methods used
Research consisted of a series of greenhouse and rain-shelter experiments aimed at understanding and
improving the protected cultivation of Actinotus helianthi. The project investigated disease control,
agronomic practices for improved growth, use of gibberellic acid to increase stem length, propagation
and methods to improve post-harvest characteristics.
Results/key findings
The key impediments to cultivation in developing a commercially viable production system for flannel
flowers were overcome.
(A) Control of root diseases
Thirty potential pathogens were isolated from random samples. Suspected fungal pathogens included
Fusarium sp. (14 isolates), Pythium irregulare (8 isolates), Pythium mastophorum (2 isolates),
ix
Pythium sp. (2 isolates), Pythium spinosum (2 isolates), Pythium sulcatum (1 isolate) and Rhizoctonia
sp. (1 isolate).
All isolates were found to be pathogenic, to varying degrees, although there were very few deaths. All
pathogens caused moderate to severe root damage. Most also caused a significant reduction in top
growth. Overall Pythium isolates were found to be more pathogenic (damaging) than Fusarium
isolates. This trial also found that often two or more pathogens may be acting together, e.g. dry weight
and root score were more severely affected by a combination of Fusarium sp. and Pythium sp. than the
individual strains.
Improving growing medium aeration was the only method of control that was commercially effective.
A number of fungicides were trialled but none were found to be useful. Production of plants under
protected cultivation assisted the control of diseases by improving root aeration (by control of
irrigation) and by keeping leaves dry.
(B) Cultural conditions
Contrary to previously published recommendations Actinotus was found to be very responsive to
applied fertiliser, especially nitrogen, and able to tolerate very high levels of added phosphorus –
unlike many Australian native plants. This is unusual as these plants evolved in soils very deficient in
phosphorus. Increasing fertiliser rates in plants previously used for commercial production greatly
improved growth rates and yields.
It was also discovered that Actinotus helianthi possess cluster roots, similar to those found in many of
the Proteaceae (previously called proteoid roots) and in a few other species in a range of plant
families. As in the Proteaceae, these probably have a key role in the mineral nutrition of Actinotus,
especially for phosphorus nutrition.
Additionally, Actinotus has shown to be adaptable to a wide range of growing media if well aerated.
This allows for a significant reduction in production costs by enabling low cost components to be
used. Actinotus can tolerate high levels of salt in irrigation water but growth is reduced even at very
low levels.
(C) Increased stem length through application of gibberellic acid
The dwarf clone was found to be gibberellin deficient. As a result, application of relatively low
quantities of gibberellin every six weeks was very effective in increasing stem length. The optimal rate
was 20ppm. Excessive rates were found to cause unacceptably weak stems.
(D) Improved propagation efficiency
Flannel flowers have a well-deserved reputation for being difficult to propagate. Tissue culture is slow
and expensive due to technical difficulties in deflasking plants. Propagation by cutting is also
relatively difficult and does not perform well so this project has concentrated on seedling material.
Initially, less than 1% of seed actually germinated, which is in keeping with published results.
Methods trialled to overcome seed dormancy including smoked water and growth regulators were
generally ineffective. Eventually the problem was solved by selecting a seedling line that had little or
no dormancy that now provides plants to growers with a viability of around 90% and a germination
percentage of over 80% in 6 weeks.
The seed propagated material performs well, producing over 600 flowering stems per square metre
annually. It has proven to be a very profitable crop given the excellent prices received on both the
domestic and export markets. For all but two growers, losses were generally low (<5% per year).
Losses were mainly caused by pathogens in (untreated) irrigation water and inappropriate growing
methods. The cutting material for the remaining growers has been replaced with seedling material. The
major disadvantage of the seedling material is its variability; but propagules are about one-third the
cost of tissue cultured material.
x
In addition to the existing seedling clone, four tissue cultured clones of elite seedlings were selected
for trialling for cut flower production. These clones were not commercial due to the low number or
complete absence of flowers.
Industry and Investment NSW and the Royal Botanic Gardens both have a range of other plants that
are not in common cultivation and have shown particular promise. New hybrids of Actinotus,
Anigozanthos hybrids and Macropidia were trialled to provide an expanded product range. Of the
plants trialled, the Anigozanthos hybrids showed particular promise with high yields on an area basis.
Growers are now producing these plants commercially for cut flower production.
(E) Post-harvest characteristics
Results showed that none of a range of common vase preservative solutions increased the vase life of
Actinotus, in fact some of them (silver ions) significantly reduced flannel flower vase life. It was found
that flannel flowers grown under protected cultivation and handled correctly have a commercially
acceptable vase life without the use of preservatives.
Implications for relevant stakeholders
This project has shown that flannel flower in protected cultivation is a profitable new product for the
Australian native cut flower industry. As a result of this project, fifteen growers are now producing
flannel flower as a cut flower crop in protected cultivation. To date, over 30,000 plants have been
distributed to growers for trialling and large quantities of seedlings have also been propagated by the
co-operators from the material initially provided. The opportunity now also exists to expand the
industry by introducing other new crops in a similar system.
Recommendations
This project has achieved a commercially viable outcome but needs continued development to
maintain the competitive advantage of the industry.
The main areas of cultural requirements, propagation, breeding and marketing require further research
such as:
•
•
•
•
•
•
fertiliser and watering studies to advance optimised growth rates
trials to define optimal growing conditions
improved tissue culture methods to enable the use of clonal materials for flower production
continued development of seedling lines to improve flower numbers and quality
identification of the breeding systems of Actinotus and investigating other species such as A.
schwarzii in a breeding program
development of cultivars and seed lines within the private industry sector.
xi
1. Introduction
The flannel flower is one of the most recognised natives of Australian flora, with attractive white
flowers and grey-green foliage of a flannelly texture. The most commonly known variety is Actinotus
helianthi, the Sydney or eastern flannel flower. This variety has long, straight stems with terminal
flowerheads that make good cut flowers and have been available commercially for many years.
To date, most of this stock has been sourced from bush-picked plants that tend to vary greatly; in
addition, availability of bush-picked stock is diminishing with the spread of urban development. These
factors have led to an increase in commercially cultivated flannel flowers from selected stock and seed
material.
Despite the production problems often encountered, flannel flowers are still a profitable crop for many
growers. Overcoming these cultivation difficulties will lead to increased production levels. Although
this would eventually result in reduced returns by lowering the average price, low total production
levels pose a greater risk to the marketability of the crop in the short term.
Flannel flowers with their relatively short plant-to-harvest period can be grown intensively and have
the potential to provide an excellent cash flow from a small land area. This applies in particular to the
continuously flowering clones that are used as a complementary crop to many other native flower and
foliage crops with extended harvest periods and greater land requirements.
Flannel flowers have developed a reputation for being difficult to cultivate – but significant advances
have been gained from work by Cathy Offord and Lotte von Richter of the Royal Botanic Gardens in
Mt Annan, as well as input from participants of the Flannel Flower Forum and a Review of Cultivation
Practices held in June 2001 (see Jones and Worrall 2001).
This project aimed to overcome impediments to the profitable commercial production of flannel
flowers (Figure 1.1). A series of greenhouse experiments (Figures 1.2 and 1.3) investigated many
aspects of Actinous production, such as disease control, agronomy, use of gibberellin to increase
flower stem length, propagation and post-harvest methodologies.
Figure 1.1 Commercial production of Actinotus following this project
1
Figure 1.2 Greenhouse purpose-built for the production of Actinotus flowers
Figure 1.3 Actinotus being grown in pre-existing greenhouse
The information presented here for the production of flannel flower in protected cultivation could also
be used to assess other potential crops.
2
2. Flannel Flower Diseases
2.1
Introduction
The flannel flower (Actinotus helianthi) has a reputation as being unreliable in cultivation, owing
mainly to its susceptibility to root diseases (Carson 2000; von Richter and Offord 2000; Wriggley and
Fagg 2003). The so called ‘damping-off’ diseases which cause plant wilting in a wide range of species
are often due to species/variants of Pythium, Phytophthora, Rhizoctonia and Fusarium. These are
quite common in nursery situations and generally where plants are grown in containers.
Cylindrocladium, Thielaviopsis and Sclerotinia may also be important in similar situations (Hartman
et al. 1997; Handreck and Black 1994).
Actinotus helianthi belongs to the family Apiaceae, which also includes common crops such as
Daucus (carrot) Apium (celery) and Pastinaca (parsnip). Internationally, there are more than seventy
pathogens known to cause root rot in commercial Apiaceae crops. Of these pathogens, those known to
be present in Australia include the true fungi from the genera Thielaviopsis, Sclerotinia,
Cylindrocarpon, Rhizoctonia and Macrophomia, as well as pathogens from the genera Phytophthora
and Pythium that are now classified as oomycetes (CAB International 2008).
In Australia, there are records of many organisms causing root diseases that affect Apiaceae such as
Thanatephorus cucemeris (teleomorph of Rhizoctonia solani), which causes damping off;
Phytophthora spp. (including P. cryptogea causing tomato root rot); Sclerotinia sclerotiorum, causing
collar rot; Pythium spp.; and Thielaviopsis basicola (syn. Chalara elegans) causing black root rot
(CAB International 2008).
Previously, the only published record of any positively identified root disease affecting A. helianthi
was Fusarium oxysporum. This had been isolated from diseased flannel flowers growing in research
plots at Mt Annan Botanic Gardens which exhibited symptoms of wilting, stunted growth and/or
vascular browning. Isolates from these plants were used to inoculate test plants to confirm
pathogenicity and the same symptoms were reproduced in some instances (Bullock et al. 1998). But
many inoculated plants remained without symptoms and Fusarium was also isolated from some of the
controls (uninoculated plants) in these trials. One of the most serious problems arising from field trials
by von Richter and Offord (2000) on Actinotus helianthi was the frequent incidence of what they
referred to as Fusarium wilt. It has also been stated that Actinotus helianthi is prone to root or wilt
diseases thought to be associated with Fusarium, Pythium or Phytophthora sp. but with no supporting
evidence (Carson 2000). In contrast, Fraser (1956) found that the common root pathogen
Phytophthora cinnamoni was associated with the roots of Actinotus helianthi plants even though they
showed no symptoms and appeared healthy. Therefore it is possible that potential pathogens can be
present on plants without those plants showing obvious symptoms.
A wide range of factors can affect the pathogenicity of root rots, such as ‘strain’ of both pathogen and
host, growing temperature, water relationships (e.g. air space in growing medium) and method of
disease transmission – especially the form of inoculum (Carling and Leiner 1990; Brayford 1992;
Kovacikova 1993; Handreck and Black 1994; Hisiang et al. 1995; Hartman et al. 1997; Kumar et al.
1999; Raftoyannis and Dick 2006; Ploetz 2004). A plant growing in favourable environmental
conditions may be left unaffected by potential pathogens.
3
2.2
Survey of A. helianthi diseases
Since this project commenced, twenty-nine Actinotus plants showing wilt and/or root rot symptoms
have been submitted to the Plant Health Disease Service of Industry and Investment New South Wales
(I&I NSW), largely from project participants. Fusarium sp. and/or Pythium sp. were isolated from all
samples (Table 2.1) and in twenty-one cases both Fusarium and Pythium were isolated from the root
system. It is possible that some or all of the remaining eight samples also had both organisms but there
was a failure to isolate and identify them.
Where the species were identified, the Fusarium isolated was F. oxysporum and the Pythium were P.
irregulare, P. mastophorum and P. spinosum. The relative contribution of Fusarium and Pythium to
the symptoms could not be determined as there are many species and races of each which may have
different pathogenicities to Actinotus. Since only one of either Fusarium or Pythium was isolated from
eight of the samples, it seems probable that either may be pathogenic enough on its own to cause
disease symptoms in Actinotus.
Rhizoctonia sp. (three instances) and possibly Cylindrocarpon sp. (one instance) appear to be the only
other potential pathogens but they also occurred in combination with Fusarium and Pythium, so it was
not possible to determine their relative contribution to the observed symptoms.
In many ways the range of root diseases affecting Actinotus helianthi appears to be similar to that of
subterranean clover. Pythium irregulare and Fusarium oxysporum were the fungi most often isolated
from diseased roots of clover during field trials in Western Australia (Wong et al. 1985). F.
avenaceum, Pythium irregulare, Pythium spinosum and Rhizoctonia solani were found to be highly
pathogenic to subterranean clover seedlings with Fusarium oxysporum less pathogenic.
Pythium irregulare and Fusarium sp. were also the most common fungi isolated from the roots of
Actinotus helianthi in this project. Fusarium oxysporum was considered to be a weak pathogen by
itself and much more aggressive in the presence of other potentially pathogenic fungi.
During the course of this study, a number of diseased plants were collected from growers and tested
for pathogenicity. In a follow-up trial, it was confirmed that the organisms isolated from the diseased
plants were pathogenic when the selected organism was re-inoculated back onto apparently diseasefree flannel flowers.
4
Table 2.1 Potential pathogens identified by the Plant Disease Health Service (I&I NSW)
5
PHDS
Accession No.
Date
01/48
21/01/2003
01/412
15/05/2001
Pythium irregulare and Fusarium sp.
Camden
wilt & root rot
01/826
4/09/2001
Fusarium sp. and Scairid fly larvae
Myall Lakes
wilt & root rot
01/1146
23/11/2001
Fusarium oxysporum and Pythium mastophorum
Central Coast
wilt & root rot
02/247
12/03/2002
Pythium sp. and Fusarium sp.
Central Coast
wilt & root rot
02/427
8/05/2002
Pythium sp.
Central Coast
dieback & root rot
02/931
13/11/2002
Fusarium sp. isolated
Myall Lakes
discoloured lower leaves & root rot
03/120
7/02/2003
Fusarium sp.
Central Coast
wilt & root rot
03/327
2/05/2003
Rhizoctonia sp. observed; Pythium sp. & Fusarium sp. isolated
Central Coast
wilt & root rot
03/420
30/05/2003
Pythium sp. and Fusarium sp.
Southern Highlands
wilt & root rot
03/425
2/06/2003
Rhizoctonia sp., Fusarium sp., Pythium mastophorum, Pythium sp.
Southern Highlands
wilt & root rot
03/651
19/08/2003
Fusarium oxysporum and Pythium irregulare
Mid North Coast
wilt & root rot
03/768
25/09/2003
Cylindrocarpon sp., Fusarium sp. and Pythium sp.
Central Coast
wilt & root rot
03/778
2/10/2003
Pythium irregulare, Pythium spinosum and Fusarium oxysporum
Mid North Coast
dieback & root rot
03/781
2/10/2003
Pythium irregulare and Fusarium oxysporum
Central Coast
dieback & root rot
03/896
6/11/2003
Pythium irregulare and Fusarium sp.
Mid North Coast
wilt & root rot
03/897
6/11/2003
Pythium sp. and Fusarium sp.
Mid North Coast
wilt & root rot
03/1000
12/12/2003
Fusarium sp. and Pythium sulcatum
Southern Highlands
wilt & death
04/121
17/02/2004
Fusarium sp.
Central Coast
brown roots
04/241
30/03/2004
Fusarium sp. and Pythium irregulare
Central Cost
swollen stem base
04/324
7/05/2004
Pythium irregulare and Fusarium sp.
South Coast
root rot
Pathogen/pest recorded
Fusarium sp. and beetle larvae
Location (NSW)
Mid North Coast
Clinical symptoms
wilt & hollow stem base
04/606
8/09/2004
Pythium irregulare and Fusarium sp.
Southern Highlands
wilt & root rot
04/622
16/09/2004
Fusarium sp., Pythium irregulare and Pythium spinosum
Mid North Coast
dieback & root rot
04/623
16/09/2004
Pythium sp. and Fusarium sp.
Central Coast
5 pots dieback & root rot
05/941
13/01/2005
Pythium irregulare and Fusarium sp.
Central Coast
wilt & root rot
05/220
2/03/2005
Pythium spinosum
Mid North Coast
wilt, stunted
05/326
24/03/2005
Pythium irregulare
Southern Highlands
wilt & root rot
05/547
22/06/2005
Pythium irregulare and Fusarium oxysporum
South Coast
plants declining
06/645
23/08/2006
Fusarium sp., Pythium irregulare and Rhizoctonia sp.
Central Coast
wilt & root rot
2.3
Trials with potential pathogens
Three experiments were undertaken to assess the effect of potential pathogens on Actinotus helianthi.
Plant growth, disease expression and pathogenicity of fungal isolates from diseased flannel flowers
were examined in the trials.
2.3.1 The effect of potential pathogens, growing medium and watering regime
on the growth of A. helianthi
Introduction
The aim of this trial was to examine the effect of a number of potential pathogens, two growing media
and two watering regimes on the growth of A. helianthi.
Materials and methods
Two potential pathogens Pythium mastophorum (isolate number 01/1146) and Fusarium (isolate
number 03/48) isolated from diseased flannel flowers were applied to apparently healthy plants
growing in pots in a plastic house. Other potentially pathogenic isolates from other species were also
included in the trial (Table 2.2). The plants used were seedlings of selection C1 grown in 700 ml pots
filled with either a well-drained mix or a heavier less well draining mix. Half of the pots were placed
in a saucer to hinder drainage even more, adding further stress to the roots. There were sixteen
replicates per treatment.
Plants were subsequently grown in an environmentally controlled greenhouse (24oC maximum during
the day, 13oC minimum at night) and irrigated with potable chlorinated water. The plants were
harvested in July 2003 and the following measurements were taken:
•
•
•
plant health score 0–5 (0 worst, 5 best)
plant dry weight
plant height.
Treatments
(a) Potential pathogens
There were a total of six pathogen treatments, including the control (Table 2.2). All pathogens were
grown on potato dextrose agar (PDA) plates. The control consisted of uninoculated PDA plates. The
plates were inoculated between 28 March and 2 April 2003 and the inoculum was applied to the plants
on 10 April 2003. The inoculum was made by macerating the agar with the pathogen (or plates alone
for the control) in 4 litres of water and then 50 ml of the resulting solution was added around the base
of each plant.
Table 2.2 Potential pathogen, accession number and source plant
_______________________________________________________________________
(*)
Potential pathogen
Accession no.
Source plant
______________________________________________________________________________
Control (no application)
Fusarium
03/48
Actinotus helianthi
Pythium mastophorum
01/1146
Actinotus helianthi
Phytophthora cryptogea
n.a.
Boronia sp.
Rhizoctonia
99/806
Anigozanthos sp. (kangaroo paw)
Thielaviopsis
n.a.
Viola x Wittrockiana (pansy)_____
(*) Accession no. is the accession number of the Plant Health Disease Service (I&I NSW)
6
(b) Growing medium
The pots were filled with one of two different growing media:
• Medium A
This medium is similar to that used commercially to grow a wide range of Australian native
plants. It is composed of equal proportions by volume of aged pine bark (Pinus radiata) fines
(<25mm), washed medium sand, horticultural grade perlite and sphagnum peat. Fertilisers added
per litre (L) of medium were: agricultural lime (0.5 g), dolomite (0.5 g), IBDU (0.5 g), Nutricote®
(Yates Australia) type 27 controlled-release fertiliser (4 g, on a % fertiliser basis N18.0: P2.6:
K6.0: Ca2.1: Mg1.2: Fe0.2: Mn0.6: Cu0.05: B0.02: Mo0.02: Zn0.015, 270-days release at 25oC
formulation) and Nutricote® coated potassium sulphate (0.5 g). The medium was then heated with
aerated steam and maintained at 60°C for 45 minutes and had a final pH of 5.5.
• Medium B
This medium represents a heavy medium with less air space than medium A. Similar components
to medium A were used but with 20% of the medium made up of a 20% Narara loam (80% fine
sand, 20% loam) so 20% of each component represented a heavy mix. The rate of agricultural
lime and dolomite was also reduced to 0.4 g/l giving a final pH of 5.5. All other fertilisers were
included and steam treatment applied as in medium A.
(c) Watering
All pots were watered three times a week by trickle irrigation. After application of inoculum, the pots
either drained freely (low watering) or were placed on a saucer (10 mm deep) to reduce drainage (high
watering) where excess water drained off the saucer to waste. During every irrigation session,
sufficient water was applied to ensure that all saucers filled up and all plants received the same volume
of water.
Results
Statistical methods
An analysis of variance (ANOVA) of weight was conducted (Table 2.3). The appropriate analysis for
root score was a generalised linear model with multinomial error distribution. With an initial
assessment of the data, the scores were assumed to follow a normal distribution and an analysis of
variance was performed.
A 2x2x6=24 level factor named treatment was created and a further ANOVA was conducted without
the factorial structure. The analysis of variance is presented in Table 2.3.
In both cases only the main effects of mix (growing medium), saucer (saucer placed or not placed
under pot) and disease (effect of inoculum) were significant (P< 0.05).
Plants grown in the ‘light’ medium had a significantly higher average dry weight (5.8 g) and root score
(3.7) than those grown in the ‘heavy’ medium (4.5 g dry weight, root score 3.2) as did those grown
without a saucer (7.2 g dry weight, 3.8 root score) compared to those grown with a saucer (6.5 g dry
weight, 3.1 root score). Growth and root health was best in the light weight mix and no saucer.
With regard to pathogens, only Phytophthora significantly reduced dry weight although both Pythium
and Phytophthora reduced root score (Table 2.4).
7
Table 2.3 Analysis of variance for weight and root score
Variate: plant top weight
Source of variation
Rep stratum
Rep.*Units* stratum
Mix
Saucer
Disease
Mix Saucer
Mix Disease
Saucer Disease
Mix Saucer Disease
Residual
Total
df
15
ss
60.80
ms
4.05
vr
40.94
1
1
5
1
5
5
5
345
383
460.70
38.97
295.00
3.91
45.59
40.45
9.04
1489.04
2443.50
460.70
38.97
59.00
3.91
9.12
8.09
1.81
4.32
106.74
9.03
13.67
0.91
2.11
1.87
0.42
df
15
ss
40.58
ms
2.70
vr
5.86
1
1
5
1
5
5
5
345
383
24.00
48.17
72.08
1.76
4.09
3.36
0.40
159.30
353.73
24.00
48.17
14.42
1.76
0.82
0.68
0.08
0.46
51.98
104.31
31.22
3.81
1.77
1.46
0.17
Variate: root score
Source of variation
Rep stratum
Rep.*Units* stratum
Mix
Saucer
Disease
Mix Saucer
Mix Disease
Saucer Disease
Mix Saucer Disease
Residual
Total
F pr.
<0.001
0.003
<0.001
0.342
0.063
0.098
0.836
F pr.
<0.001
<0.001
<0.001
0.062
0.118
0.203
0.973
Key: df = degrees of freedom, ss = sum of squares, ms = mean square, vr = variance ratio, F pr. = probability of
the F value.
Table 2.4 The effect of pathogen and disease on dry weight and root score
Parameters
measured
Dry wt. (g)
Root score
Control
7.19
3.828
Fusarium
7.17
3.656
Treatments
Phytophthora Rhizoctonia
4.09
7.15
2.531
3.609
Pythium
7.04
3.500
Thievaliopsis
7.54
3.719
lsd
0.78
0.237
Re-isolation
An attempt was made to re-isolate the organism from the infected pots for four of the replicates. Of the
plants sampled for the applied pathogens, only Fusarium, Rhizoctonia, Pythium and Phytophthora
could be re-isolated from the roots. Attempts to re-isolate Thielaviopsis were negative.
Conclusions
Reducing aeration by either growing plants in a heavy mix or by placing a saucer under the pots
reduced the growth of the plants. However, there was no interaction with disease expression as may be
anticipated from the published literature, i.e. reduction in aeration did not make disease more severe.
Fusarium, Rhizoctonia, Pythium and Phytophthora were re-isolated from the roots of infected plants.
Thielaviopsis was not re-isolated, but this did not indicate whether it is non-pathogenic to A. helianthi
or if the fungi failed to establish. Fusarium and Rhizoctonia, although established in the growing
medium, did not affect the plants. Under conditions of greater stress the possibility remains that they
may be pathogenic.
8
2.3.2 The effect of potential pathogen and method of inoculation on disease
expression
Introduction
Method of inoculation is known to be important in the induction of root diseases. The aim of this trial
was to compare two methods of culturing the disease inoculum before it was added to A. helianthi
growing in pots. The isolates were grown either on PDA agar plates or on millet grains.
Materials and methods
Fusarium (isolate number 03/425) and Pythium mastophorum (isolate number 01/1146) isolated from
flannel flowers were used in this experiment. The isolates grown on agar plates were treated by adding
the contents of the plates to distilled water and macerating with a hand-held blender. Then 50 ml of the
solution was added to each pot. Approximately 1 gram of inoculated millet grains were added to the
pots via three holes that were made around the plant.
The isolates were added both alone and in combination. Where both Fusarium and Pythium were
added to the pots, 50 ml of each isolate or 1 g each of inoculated millet grains were used. The control
was a solution of uninoculated PDA plates added to distilled water and macerated prior to applying to
the pots.
The plants were gown in 100 mm pots without saucers in the greenhouse used in experiment 2.3.1.
The inoculum was added to pots on 10 April 2003 and material was harvested three weeks later.
Treatments were applied in a factorial structure of nine treatments (4 x 2 factorial + control) as shown
in Table 2.5. Dry weight and survival data were collected at the end of the trial.
Table 2.5 Pathogens and carrier used in experiment 2.3.2
Pathogen
Nil
Fusarium
Pythium
Fusarium + Pythium
Nil

Media
Agar
Millet








Key: = combination used.
Statistical analysis consisted of a randomised block design with four blocks using eight or nine
replicates of each treatment per block. Blocks 1, 3 and 4 included eight replicates and Block 2
comprised nine, resulting in thirty-three repeats of each treatment. The experimental unit was a single
plant in a pot. Since the design was unbalanced, ASReml was required to analyse the data. Several
plants died due to the treatment so a dry weight of zero was recorded for those.
Results
Survival
Survival was analysed as a generalised linear model with binomial errors and logit link fitted to the
data. Plant survival was lowest for the Fusarium + Pythium on agar treatments (29/33=0.88) and
Pythium on agar (30/33=0.91) but there was no significant effect of treatment on survival proportion
(P<0.05).
Re-isolation
Both potential pathogens were re-isolated from the growing medium.
9
Dry weight
Significant main effects on plant dry weight of pathogen and media were observed, with the
interaction between the two also significant (P<0.05). The dry weight interaction means are shown in
Table 2.6 below. For Fusarium on its own there was no significant effect of media type on dry
weights. For Pythium and the combination of Fusarium and Pythium, dry weights were significantly
less for plants in the agar treatments. There was no significant effect (P=0.05) of media type on the
control treated plants.
Table 2.6 Predicted dry weight means
Pathogen
Nil
Fusarium
Pythium
Fusarium + Pythium
Average SED
Average LSD (P=0.05)
Media
Agar
10.46
10.26
8.12
7.48
Nil
10.85
Millet
10.39
9.47
10.54
10.39
0.725
1.450
Conclusions
Method of inoculation did have an effect on disease expression, at least for Pythium in this trial where
agar inoculum was more effective than millet inoculum. Fusarium did not either reduce dry weight or
survival, despite having been isolated from plants showing disease symptoms. There was also no
synergistic effect between the two potential pathogens; this is discussed in more detail below.
2.3.3 Determining pathogenicity of fungal isolates from diseased A. helianthi
Introduction
The aim of this trial was to determine the pathogenicity of all available fungal isolates from diseased
A. helianthi (Table 2.7) under conditions that had previously been found to maximise expression of the
disease.
Materials and methods
Actinotus helianthi (Labill) seedlings of variety C1 (Gosford HRAS) were planted in 125 mm pots
containing 300 ml of a growing medium composed of equal portions of composted pine bark fines,
sphagnum peat, perlite and medium sand all adjusted to a pH of 5.5. A slow-release fertiliser (3.3
kg/m3 of Nutricote ® 17% N, 6-months release at 25oC) was also added. Plants were then grown in a
greenhouse (50% shade, 15oC night minimum, 26oC day maximum). There were ten plants per
treatment.
10
Table 2.7 List of potential pathogens in experiment 2.3.3
Fungi
Control
*Fusarium sp.
*Fusarium sp.
*Fusarium sp.
*Fusarium sp.
*Pythium mastophorum
*Fusarium oxysporum
*Rhizoctonia solani
*Fusarium sp.
*Pythium spinosum
*Fusarium sp.
*Fusarium sp.
*Fusarium sp.
*Pythium irregulare
Pythium irregulare
*Fusarium sp.
*Pythium sp.
*Pythium sulcatum
*Fusarium+ *P. irregulare
Fusarium oxysporum
*Pythium irregulare
*Pythium mastophorum
*Pythium irregulare
*Pythium irregulare
*Pythium spinosum
*Pythium irregulare
*Pythium sp.
*Pythium irregulare
*Pythium spinosum.
*Pythium. irregulare
*Pythium irregulare
lsd (P=0.05)
F value probability
Accession no.
n.a.
(04/121)
(04/623#5)
(03/1000)
(01/826)
(03/425)
(05/547a)
(03/778)
(04/324)
(03/778)
(04/241)
(04/622#1)
(01/48)
(04/623#5)
(02/435)
(04/622#2)
(03/425)
(03/1000)
(04/623#5)+(04/623#5)
(03/651)
(03/651)
(01/1146)
(03/778)
(04/324)
(05/220#3)
(03/768A)
(03/897)
(03/781)
(04/622#1)
(04/241)
(01/412)
Root
score
3.796
3.364
3.356
3.206
2.975
2.796
2.753
2.716
2.644
2.523
2.510
2.455
2.376
2.375
2.372
2.279
2.258
2.155
2.089
1.971
1.956
1.940
1.876
1.842
1.805
1.697
1.634
1.608
1.579
1.110
1.090
0.683
<0.01
Figure 2.1 General view of experiment 2.3
11
Top dry
wt. (g)
4.4
2.5
2.5
2.3
2.2
2.7
2.2
1.9
1.5
1.3
1.4
1.3
1.9
1.8
1.4
1.4
1.1
1.8
1.3
1.4
1.4
1.5
1.1
1.3
1.5
1.0
1.3
1.0
1.5
0.8
0.9
0.694
<0.01
Inoculum was grown on agar plates with oat pieces. Plate contents were added to distilled water,
macerated with a hand-held blender until roughly mixed and 50 ml of the resultant mixture was poured
onto the top of the soil around each plant. The control was made by macerating uninoculated plate
contents with distilled water and adding 50ml of this mixture to the pots. The plants were inoculated
on 3 July 06.
At the time of inoculation, the roots of the plant were damaged by stabbing the root zone in order to
aid infection.
As the plants continued to remain healthy, it was decided that they would be re-inoculated with the
same isolates. On 19 July 06 the plants were potted into 100mm pots prior to re-inoculation and a
saucer was placed below each pot to increase waterlogging.
On 2 August 06, the dry weight of plants and root score were assessed as in experiment 2.3.1. An
attempt was made at the end of the trial to re-isolate the potential pathogen from all treatments.
Results
Pathogenicity
All isolates significantly (P< 0.05) reduced root scores (see Table 2.7) indicating that the pathogen
damaged the root system. The dry weight of all inoculated plants was reduced, except for the dry
weight of the plants inoculated with the three Fusarium sp. which did not significantly reduce below
that of the uninoculated control. So although the roots may be damaged, dry weight of the plant
representing growth may not be greatly reduced. It is clear that environmental conditions, including
inoculum type, may also be important in disease expression. In experiment 2.3.1, Fusarium isolate
number 01/48 did not significantly reduce dry weight but in this experiment it significantly reduced
both dry weight and root score. In contrast, Pythium mastophorum (isolate number 01/1146)
significantly reduced dry weight in both experiments.
Figures 2.2 and 2.3 illustrate the effect of root disease on Actinotus.
Figure 2.2 The effect of root disease on Actinotus.
Left: uninocculated control. Right: diseased plant.
12
Figure 2.3 Root systems showing the effect of diseases.
Left: unaffected root system, Right: roots have been largely destroyed by disease.
A linear regression of dry weight on root score was also calculated and the two were highly correlated
(Figure 2.4).
Fitted and observed relationship
5
Dry Weight (g)
4
3
Y= 4.13-3.8 (0.61X)
(55% of total variance
accounted for)
2
1
0
0
1
2
3
Root Score
4
5
Figure 2.4 Dry weight versus root score. As root damage increased, growth rate was reduced.
The fitted response equation and percentage of the total variance accounted for by the model
are shown on the graph.
13
Re-isolation
All fungi used in the trial were re-isolated at the end of the trial from their respective treatments.
Conclusions
During the course of this project a large number of flannel flowers with apparently diseased roots were
examined at Elizabeth Macarthur Agricultural Institute. Often two or more potential pathogens,
especially Fusarium sp. and Pythium sp., were detected together in root samples. It is usually practical
to only identify fungi to genus level and even if they can be identified to species level many strains
can be barely pathogenic or not at all. To further complicate the issue some non-pathogenic strains of
fungi can provide partial protection against others in the same genera by competing with them in the
plant growing medium.
The pathogenicity of the isolates was determined by inoculation of flannel flower seedlings growing in
pots in a greenhouse and measuring top growth and the quality of the root system. The pots stood in
shallow saucers to promote the development of root diseases. Pathogens were re-isolated from
inoculated pots to ensure that plants had become infected.
All isolates were found to be pathogenic to varying degrees – but there were few resultant deaths. All
pathogens caused moderate to severe root damage. Most (Experiment No. 3) also caused a significant
reduction in top growth. Overall, Pythium isolates were found to be more pathogenic (damaging) than
Fusarium isolates. This is contrary to the findings of Bullock, Summerell and von Richter (1998) and
von Richter and Offord (2000) where Fusarium oxysporum was of greater concern. The strain of
Rhizoctonia tested was also generally less pathogenic than the Pythium tested.
These trials demonstrated that all isolated fungi could be pathogenic. This is especially true of
Fusarium sp. and Pythium sp. There is little evidence in these experiments to show that the diseases
are synergistic. One group of plants was inoculated with both a strain of Fusarium sp. and a strain of
Pythium sp. The resultant dry weight and root damage scores were not significantly different from
plants inoculated with the same strain of Pythium alone. This is unlike the case in subterranean clover
where they were found to be synergistic (Wong et al. 1985). Further testing would be required to
confirm whether the effect of Pythium and Fusarium is synergistic or not.
Phytophthora was found to be pathogenic in the experiment reported on in section 2.3.1. Previously,
Fraser (1956) had found Phythphora cinnamoni to be non-pathogenic to Actinotus
in the field. This trial (experiment 2.3.1) demonstrated that, under more adverse conditions,
Phytophthora could become pathogenic. Another possibility is that they were different strains with
different pathogenic potentials as has been shown for both Fusarium and Pythium.
The only commercially effective method of control was found to be by cultural methods i.e. improving
growing medium aeration. A number of fungicides registered for the control of these diseases were
trialled (in an experiment not reported here); however, none were found to be effective. Production of
plants under protected cultivation has the dual advantage of assisting in controlling root diseases by
enabling better management of root aeration (by control of irrigation) and helping to prevent foliage
diseases by keeping leaves dry.
14
3. Plant Nutrition
3.1
Response of flannel flowers to fertilisers
Introduction
Flannel flowers naturally grow on soils of low fertility (Beadle 1966) and are considered to be
fertiliser sensitive (Offord and Tyler 1996). Despite this, they appear to tolerate a wide range of
nutrient levels in their growing medium, flourishing in most areas where they have been trialled,
except one site which was observed to have an exceptionally high soil phosphorus level, i.e. 291.9
meq% (von Richter and Offord 1997). Despite this, leaf chlorosis, which is indicative of nutrient
deficiency, is often observed on flannel flowers in cultivation especially when they are growing in pots
or on clay soils (Offord and Tyler 1996). This is generally considered to be caused by an induced iron
deficiency when there is poor root health, high pH or iron bound up by excessive levels of other
elements, particularly phosphorus.
Previous container trials have shown that flannel flowers respond well, in terms of vegetative growth
and flower production, to the application of complete fertilisers. In one trial, the upper limit of the
response to fertiliser application was not reached even though twice the normal rate for ‘fertiliser
tolerant crops’ was applied (i.e. 10 kg/m3 of Nutricote ® slow-release fertiliser N13: P2.6: K10.8 or
N18: P2.6: K6.6, 9-month formulation). Plants were larger and flower stems more numerous with a
greater number of floral bracts as the rate of fertiliser increased but there was apparently no response
to added P (von Richter and Offord 1997).
There is a need to determine the optimum rates of both N and P in the growing medium for the
commercial production of flannel flowers. There is a lack of published leaf tissue standards for N and
P as well as other essential elements for plant growth – this should also be addressed in order to
provide a guide for better fertiliser management of crops. The following trial examined the effect of N
and P fertilisers on the growth of flannel flower under typical commercial growing conditions with the
aim of determining the optimal rate for both N and P with respect to growth rate.
Materials and methods
(a) Fertilisers
N was added as coated ammonium nitrate (CAN) – Osmocote ® CAN 23% N (as a nominal 5-month
release formulation) at the rates of 2, 5, 8 and 11 g per litre. P was added as single superphospate (9%
P) at the rates of 0, 0.0625, 0.125, 0.25, 0.5, 1, 2 and 4 g superphosphate per litre. N and P levels were
applied as a factorial with ten replicates.
(b) Potting medium
Plants were grown for three months in 150 mm pots containing 600 ml of a standard growing medium
composed of equal proportions (by volume) of composted pine bark fines, sphagnum peat, perlite and
coarse sand. Coated potassium sulphate was added at the rate of 1.5 g /l, Micromax ® trace element
supplement at the rate of 0.5 g /l and the pH was adjusted to 6.0 by the addition of dolomite.
(c) Planting material and growing conditions
Plant material consisted of tubed seedlings of a selected early flowering A. helianthi (variety C1). The
plants were grown in a greenhouse with 50% shade and a minimum temperature of 15oC and a
maximum temperature of 17oC for five months. Plants were irrigated by overhead spray as required.
15
(d) Measurements
At the termination of the trial the dry weight of the aerial portion of the plants was measured. N, P and
other tissue levels of a range of elements in the leaves essential for plant growth (as listed in Table 3.1
below) was determined by CSIRO Division of Plant Industry, Canberra. Three plants from each
treatment were analysed. Plants selected were those with the highest dry weight and those closest to
the 75 percentile and 50 percentile in terms of ranked dry weight for each treatment.
Table 3.1 Leaf nutrient levels for healthy leaves
Element
(atomic
symbol)
Level
Average
Maximum
Minimum
Standard
deviation
50.69
157.79
27.09
27.99
Ca %
0.58
1.26
0.38
0.15
Cu (mg/kg)
6.77
9.29
3.44
1.75
Fe (mg/kg)
112.76
304.53
63.06
62.94
K %
1.17
1.58
0.61
0.25
Mg %
0.17
0.21
0.13
0.02
Mn (mg/kg)
180.64
371.51
59.56
84.11
Mo (mg/kg)
0.57
3.33
0.03
0.81
N%
1.97
2.56
1.45
0.25
Na %
0.37
0.68
0.21
0.13
P %*
0.05
0.43
0.05
0.12
S %
0.18
0.72
0.12
0.10
58.50
160.74
27.57
30.96
Al (mg/kg)
Zn (mg/kg)
* Optimal P% is approximately 0.1 to 0.2, as determined by growth of the plants (see above). However, there are
no obvious deficiencies or toxicity symptoms over this range and leaf P levels and plant growth rates were
highly variable.
Results and discussion
Rate of P application did not have a significant effect (P>0.05) on dry weight nor was any interaction
with the rate of N significant (P=0.05). Tissue P increased greatly with applied P, increasing from
approximately 0.05 to 0.44 % (Figure 3.1). Tissue P varied with dry weight (P=0.05). When tissue P
was regressed against individual plant dry weight (Figure 3.2) the optimal tissue level of P (i.e.
maximum dry weight) was approximately 0.15%, although dry weight was highly variable and bore
little relationship to tissue P (R2 = 0.14). From a commercial cultivation perspective, optimal tissue
level is approximately within the range 0.05 to 0.30.
16
0.50
0.45
Tissue P ( %)
0.40
0.35
0.30
0.25
0.2
Y= -0.02+0.154X+0.082X 2 (R2=0.88)
0.15
0.10
0.05
0.00
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Applied P (g superphosphate/L)
Figure 3.1 The effect of applied rate of superphosphate on tissue P level. Fitted equation and
its correlation coefficient are shown on the graph.
4.5
Dry Weight (g)
4.0
3.5
3.0
2.5
Y=1.80+5.27X-16.91X2
R2=0.14
2.0
1.5
1.0
0.5
0.0
0.0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Tissue P (%)
Figure 3.2 The effect of tissue P on dry weight. The fitted equation and its correlation
coefficient (R2) are shown on the graph.
The rate of added CAN did not have a significant effect (P> 0.05) on plant dry weight although leaf
tissue N increased slightly (P<0.05) with increasing rates of CAN (Figure 3.3). In general, leaf N
levels were between 1.5% and 2.5% with an average of 2%. Unlike P, little additional N was taken up
by the plant and accumulated in the leaf when the level of CAN in the growing medium was increased.
The lowest rate used in this experiment (2 g/l CAN) would appear to be the most economical for the
production of Actinotus.
17
3.0
Leaf N (%)
2.5
2.0
1.5
Y= 0.0297X + 1.7931
R2 = 0.1951
1.0
0.5
0.0
0.0
2
4
6
CAN (g/L)
8
10
12
Figure 3.3 The effect of CAN rate on leaf tissue N. Fitted equation and its correlation coefficient
(R2) are shown on the graph.
Conclusions
Handreck and Black (1994) recommend the addition of 0.5 g/l single superphosphate to obtain optimal
growth rates for plants not sensitive to added P. Using this criteria, flannel flower was found not to be
sensitive to added P. Actinotus is also relatively tolerant of applied N as there was no significant effect
on growth rate after added CAN supplied rates of N up to levels far in excess of those used by von
Richter and Offord (1997). Uptake of N, as determined by tissue levels also did not increase greatly
with increasing CAN levels. From this trial, the optimum rate of CAN is 2 g/l if minimum fertiliser
usage is to be taken into consideration. Overall, flannel flower has shown to be a plant with a medium
to high fertiliser requirement.
The elemental composition of leaves given in Table 3.1 could be used as a guide for ‘normal’ leaf
levels as there were no visual symptoms of toxicity or deficiency and plants appeared to be growing
normally. Further experimental work is still necessary to verify these ranges.
18
3.2
The effect of NaCl on the growth of A. helianthi
Introduction
Salinity in the growing medium due to salts in the irrigation water and/or added fertiliser can have
serious effects on plant growth and yield. Plants vary considerably in their response to salinity but
there is still a serious lack of quantitative information on salt tolerance even for widely grown crops
(Shannon and Grieve 1999). There is no published information at all on the tolerance of Actinotus to
salinity and electrical conductivity (EC) of the growing medium or soil is generally used as an
indication of its salt content and the subsequent effect on plant growth (Bunt 1976). In irrigation water,
a wide range of ions make up the salinity level and therefore EC, but in growing media common salt
(sodium chloride, NaCl) is usually the main contributor.
Commercial crops in the Apiaceae family, of which Actinotus is a member, also vary greatly in their
tolerance to salinity. Carrots, which are classed as salt sensitive, suffer from reduced yield beyond a
threshold of 1.0 dS m-1 (Shannon and Grieve 1999). Additional to an osmotic effect, specific ions may
be toxic above certain concentrations, for example, if Cl and Na ions exceed about 0.2 m they may be
toxic in themselves (Bunt 1976).
The Saturated Media Extract method (SME) used for determining the EC of organic-based growing
media is much more indicative of the actual solution in the growing medium, due to its higher
moisture holding capacity and the use of containers, than those of field soils (Bunt 1976; Cabrera
1998; Cavins et al. 2004). More recently the Pour Through (PT) technique is gaining popularity in
measuring salinity of growing media in pots due to its simplicity – because deionised or distilled water
is not used to dilute the media solution it reflects the actual medium solution more accurately (Cabrera
1998; Cavins et al. 2004). The PT technique also has the advantage of not disrupting granules of slowrelease fertiliser that are often used in potting mixes. The principal disadvantage is that salinity
standards have largely been developed for the Saturated Paste Extract (SPE) method.
Typically, PT measurements are higher than those for the SME method because the solution is not
diluted in the measurement procedure (McLachlan et al. 2004, Blythe and Merhaut 2007). Depending
on the medium measured, the value for the SPE method is around 10–40% less than the PT method
but it can be argued that the latter value more accurately reflects the actual solution in the growing
medium. Mc Lachlan et al. (2004) found that the EC on average in a wide range of composts and
potting materials (with a wide range of EC values) was 60% of the SME method with a high
correlation (R2=0.78). Cavins et al. (2004) found a similar relationship.
Table 3.2 Conductivity readings for the salinity tolerance of plants grown in organic-based
media (Bunt 1976)
Plant tolerance
Low
Medium
High
Desirable range
SME
1–2
2–4
4–6
PT
1.7–3.3
3.3–6.7
6.7–10.0
The effect of salinity is also very dependent on environmental conditions. To determine a plant’s
susceptibility to salinity, other species with a known response should be grown under similar
conditions for comparison.
The purpose of this trial was to determine the effect of salinity (NaCl) on the growth of Actinotus. For
comparison, two other species with known responses to salinity were grown under the same
conditions.
19
Materials and methods
Plants were irrigated daily with distilled water containing 0, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10, or 0.12
molar NaCl. Sufficient solution was added to ensure that at least 5% of the applied volume ran to
waste at each irrigation. Actinotus seedlings were grown for three months in 5 cm tubes containing
320 ml of a growing medium similar to that used in section 3.1 of this chapter except that 5 g/l of
Nutricote ® slow-release fertiliser (N18: P2.6:,K6.6, 9-month formulation) was added instead of CAN
and superphosphate. There were ten replicates per treatment used.
Comparator plants used were Tagetes patula L. var ‘Honeycomb’ (French Marigold) – a plant
considered to have a high salt tolerance (USDA 2009) and Dichondra repens J.R. Forst –a plant
considered to have a low salt tolerance (Harvardi et al. 2001). Plants were established from seed and
grown in a similar fashion to that of Actinotus, except that 150 mm squat plastic nursery pots
containing 600 ml of medium were used.
Results and discussion
EC (dSm-1) of the growing medium
Addition of NaCl to the irrigation water had a highly significant effect on the EC of the growing
medium as determined by the PT technique (Figure 3.4). The EC of the medium had a linear
correlation with NaCl concentration in the irrigation water. Fertilisers and other solutes in the growing
medium contributed an EC of around 1.6 dSm-1 (as determined from the Y intercept – Figure 3.4) to
the total salinity.
30
Y= 1.59+ 182.22X
R2=0.94
25
20
15
10
5
0
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
NaCl concentration in irrigation solution (molar)
Figure 3.4 EC of the growing medium compared to concentration of NaCl in irrigation water.
The fitted equation and its correlation coefficient (R2) are shown on the graph.
Increasing salinity reduced the growth rate of Actinotus helanthi, Dichondra repens and Tagetes
patula in a linear fashion. All had a similar response to added NaCl in the irrigation water up to at
least 0.08 M NaCl. The slope of the fitted equations for all species grown (Figure 3.5) were not
significantly different (P>0.05) indicating that all were equally affected by the EC of the growing
medium, whether classified as salt sensitive or not (Figures 3.5 and 3.6). It is clear that the addition of
20
any NaCl to the irrigation water will reduce the growth rate of all the species tested so in commercial
practice, salt-free irrigation water is preferable when aiming to maximise growth rate.
Key
4
Actinotus
Dichondra
3.5
Tagetes
Linear
(Actinotus)
Linear
(Dichondra)
Linear
(Tagetes)
Dry weight (g)
3
2.5
2
Y=2.47-11.0X
R2=0.56
1.5
1
Y=1.76-8.92X
R2=0.29
0.5
Y=1.88-11.9X
R2=0.71
0
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Concentration of NaCl in the growing medium (M)
Figure 3.5 The effect of NaCl on the growth of plants. Regression equations and correlation
coefficients (R2) are shown.
Handreck and Black (1994) classify plants’ sensitivity to salt on their tolerance to increasing EC in the
growing medium based on the EC level required to reduce the growth rate by 25%. Under this
classification method all three varieties would accept an EC of at least 8 dSm-1, which classifies a
plant as tolerant of salinity. For Dichondra repens this finding contrasts with its classification as salt
sensitive by Harvardi et al. (2009). Other common plants with a high salt tolerant classification are
grapes (Vitis spp) and beets (Beta vulgaris).
Levels above 0.08 M NaCl, resulted in the death of 50% of Actinotus (Figure 3.6) and both Dichondra
and Tagetes exhibited symptoms typical of excessive salinity such as leaf burn (Figures 3.7 to 3.10).
This corresponds to an EC in the growing medium in excess of 16 dSm-1 (from Figure 3.4) so on the
criteria set out in Table 3.2, Actinotus and the other two species are considered to be tolerant to high
levels of salinity.
21
100
90
Survivors (%)
80
70
60
50
40
30
20
10
0
0
0.01
0.02
0.04
0.06
0.08
0.10
NaCl concentration in the irrigation water (M)
0.12
Figure 3.6 The effect of NaCl on the survival of Actinotus
Figure 3.8 Salinity reduces the growth
of Tagetes patula. Left: low salinity.
Right: high salinity
Figure 3.7 Salinity reduces the growth
rate of Actinotus. Left: low salinity.
Right: high salinity
22
Figure 3.9 Symptoms of high salinity
(leaf burn) on flannel flower
Figure 3.10 The effect on flannel flower
plants exposed to a high level of
salinity. Note the variable effect on
plants – from no visible effect to death
23
4. Cluster Roots
4.1. Introduction
Actinotus helianthi Labill (family Apiaceae) is widely distributed naturally on the east coast of
Australia in soils usually considered to be of low to very low fertility, especially with regard to
available P (Beadle 1966). Actinotus is also successfully cultivated on sites with low levels of
available P (less than 3 mg/kg soil), although it will tolerate higher levels. Optimal aerial growth of
plants in artificial growing medium, in terms of height and number of saleable flowering stems occurs
at levels of 2 g/l or greater of slow-release fertiliser Type 27 Nutricote® (N18.0%: P2.6%: K6.0%,
270-day release at 25oC) in potting medium. Additional P does not increase aerial growth at these
levels of Nutricote® (von Richter and Offord 1997; Worrall et al. 2004).
Actinotus grows naturally in close association with a wide range of species belonging to the family
Proteaceae (Carolin and Tindale 1994), that develop cluster roots as a means of extracting nutrients
from nutrient poor soils (Lamont 2003). Cluster roots have also been described in a limited number of
species in other families: Fabaceae (Trinick 1977), Mimosaceae (Sward 1978), Casuarinaceae
(Reddell et al. 1986), Elaeagnaceae (Skene 1998), Myricaceae (Louis et al. 1990), Moraceae
(Rosenfield et al. 1991), Betulaceae (Hurd and Schwintzer 1996), and Curbitaceae (Waters and
Blevins 2000) and Monotropaceae (Young et al. 2002). Lamont (2003) describes cluster roots in detail
and predicted they would be found in other families and represent ‘one of the three major root
modifications along with mycorrhizas and nodules, among flowering plants’. There is no record in the
literature of A. helianthi or any other member of the family Apiaceae producing cluster roots, although
these could be of considerable ecological advantage to A. helianthi. Observations of cluster roots or
cluster root formation on A. helianthi growing in an artificial medium are presented as follows.
4.2
Materials and methods
Observed plant material was derived from a selected seedling of a cutting propagated semi-dwarf
clone of A. helianthi. The original parent material of the clone was collected from a coastal headland
on the Central Coast of NSW (Figure 4.1).
In June 2004, forty struck cuttings were transplanted individually into standard plastic nursery pots
containing 2 litres of medium. Plants were subsequently grown in an environmentally controlled
greenhouse (24 oC maximum day, 13 oC minimum night). The growing medium was the same
commercial potting mix used to grow a wide range of Australian native plants, composed of equal
proportions by volume of aged pine bark (Pinus radiata) fines (<25mm), washed medium sand,
horticultural grade perlite and sphagnum peat. Fertilisers added per litre of medium were: agricultural
lime (0.5 g), dolomite (0.5 g), IBDU [isobutylidene diurea] (0.5 g), Nutricote® (Yates Australia) type
27 controlled-release fertiliser (4 g, on a % fertiliser basis N18.0: P2.6: K6.0: Ca2.1: Mg1.2: Fe0.2:
Mn0.6: Cu0.05: B0.02: Mo0.02: Zn0.015, 270-days release at 25oC formulation) and Nutricote®
coated potassium sulphate (0.5g). The medium was heated with aerated steam and maintained at 60°C
for forty-five minutes and had a final pH of 5.5. Plants were irrigated with chlorinated water. Root
systems of all plants were examined on 27 October 2004. The growing medium was removed from the
root systems by gentle washing and numbers of root clusters were then counted.
24
Figure 4.1 Dwarf Actinotus helianthi growing in its natural habitat
4.3
Results and discussion
Extensive development of cluster roots was observed in all plants and formed a dense mat throughout
the growing medium, averaging 96.4 (s.e.=25.7) per plant. This is the first record of cluster root
formation in Actinotus and the family Apiaceae. Figure 4.2 (a) illustrates the development of cluster
roots on the root system with growing medium removed (NB many of the root clusters became
detached during the washing process). Individual clusters are shown in Figures 4.2 (b) and 4.2 (c).
Clusters were of the type described as ‘simple’ by Lamont (2003), i.e. they were produced on lateral
root branches with no secondary branches (Figure 4.2 (a)). The structure of the individual clusters was
similar to that described by Lamont (2003) for non-proteoid root clusters of Viminaria (Figure 4.2
(b)).
Cluster roots are known in other species to increase the uptake of soil nutrients especially P, Ca, Mn,
Fe and Zn by direct contact with the soil and through exudates that solubilise soil nutrients (Lamont
2003). The function and mode of action of the cluster roots of A. helianthi remains to be determined.
Production of cluster roots at the level of applied fertiliser especially P, for A. helianthi described here
is unusual – they are generally rare or absent in other species where nutrient conditions are optimal for
growth of the main root system and aerial portions of the plant (Lamont 2003). However, based on
observations of other cluster root producing plants it seems likely that they would also be produced at
the much lower levels of available nutrients experienced by plants growing in their natural habitat. In
the case of A. helianthi, this would contribute significantly to its ability to compete in nutrient
deficient soils. This could also explain the sensitivity of flannel flowers grown at low rates of
fertilisers to the sudden addition of large quantities of fertilisers. Plants with extensive cluster root
development may take up excessive fertiliser until this additional root formation is suppressed by the
high fertiliser rate.
25
Figure 4.2 Cluster roots on Actinotus helianthi
Figure 4.2 (b) Cluster roots with
growing medium removed and floated
in water
Figure 4.2 (a) A. helianthi with growing medium
removed showing cluster root development. Most
were detached in the washing process to remove
the growing medium. Note organic matter
embedded in cluster roots.
26
Figure 4.2 (c) Cluster root
development between the surface of
growing medium and plastic pot with
pot removed
5. The Effect of Growing Media on the
Growth of Actinotus and Other Species
5.1
Introduction
The growth and flowering of plants can be greatly affected by the growing media. For example,
nitrogen availability and utilisation can be affected by organic components while the number and size
of air spaces within the media, known as the Air Filled Porosity (AFP), can have a large effect on
growth.
There is a large range of components available for commercial growing media in Australia. Some of
the more common ones used for growing native plants are peat, coir, pine bark, perlite and sand. These
differ in their physical and chemical properties as well as price. Commercial mixtures are generally
used, as growing media based on one component don’t generally perform well for different species
and environments. Bunt (1976) also noted that mixtures of components often perform better than the
individual components. Commercially, the choice of growing media may be dictated by cost as well as
plant performance.
This trial examines the growth of a range of plants in a selection of growing media that is typical of
those used commercially. A commonly grown species Lycopersicon esculentum (tomato) with wellknown requirements was used as a comparator to Actinotus. The effect of growing media on
Anigozanthus (kangaroo paw) and Macropidia (black kangaroo paw) was also examined.
Figure 5.1 General view of initial selection pilot trials
27
5.2
The effect of growing media on growth of Actinotus and
tomato
5.2.1 Materials and methods
Actinotus helianthi cv C1 and tomato cv Gross Lisse were grown for six weeks in a greenhouse
(maximum temperature 25oC, minimum temperature 18oC) using 150 cm diameter pots with a volume
of 600 ml containing a range of growing media (Table 5.1). There were ten replicates per
variety/growing medium. Plant dry weight was analysed using a completely randomised ANOVA
design.
Six growing media were used and their components are listed in Table 5.1. All were adjusted to a pH
of 5.5 with a 1:1 mixture of agricultural lime and dolomite. Additional fertilisers added per litre of
medium were: IBDU [isobutylidene diurea] (0.5 g), Nutricote® (Yates Australia) type 27 controlledrelease fertiliser (4 g, on a % fertiliser basis N18.0: P2.6: K6.0: Ca2.1: Mg1.2: Fe0.2: Mn0.6: Cu0.05:
B0.02: Mo0.02: Zn0.015, 270-days release at 25oC formulation) and Nutricote® coated potassium
sulphate (0.5g). The medium was heated with aerated steam maintained at 60°C for forty-five minutes
and had a final pH of 5.5.
The AFP of the media was determined by the method devised by Handreck and Black (1994).
Nitrogen draw down (utilisation) of the organic materials was determined by adding potassium nitrate
to the materials after they were adjusted to a pH of 5.5 with dolomite – the nitrate level in the organic
matter was determined at the beginning of the experiment and after two weeks. The organic matter
was moistened and held at a temperature of 25oC. Five replicates for each test was used and statistical
analysis was by ANOVA.
5.2.2 Results and discussion
Plant dry weight of Actinotus and tomato was significantly affected by media (P< 0.05) as shown in
Tables 5.1 and 5.2. The peat/pine bark medium promoted the best growth in Actinotus but the worst in
tomatoes. Although tomatoes have a high requirement for fertiliser for maximum growth this does not
appear to be the reason for its poor result in the peat pine/pine bark mix. The nitrogen drawdown from
organic components in this mix could be predicted to be half of that in the peat medium where
tomatoes had maximum growth (Table 5.2). However, low AFP is also known to inhibit the growth of
tomato and was lowest in the peat/pine bark medium. In contrast, the growth of Actinotus did not
appear to be reduced by low AFP or an increased rate of nitrogen draw down.
The components varied widely in other characteristics such as buffering capacity, drainage qualities
and possibly the ability to suppress root diseases (Handreck and Black 1994). This emphasises the
need to trial growing media before it is used commercially on a large scale.
28
Table 5.1 Air Filled Porosity of growing media and the effect of media on the dry weight of
Actinotus and Lycopersicon esculentum
____________________________________________________________________________
Major Components
AFP*
Plant dry weight (g)
Name
Components
%
Actinotus
Lycopersicon
(v/v)
____________________________________________________________________________
Coir S/Sand
Coir 80%
19.0a
4.79b
3.45b
Sand 20%
Coir V/Sand
Coir 80%
Sand 20%
18.7a
5.34b
3.51b
Coir S/Peat
Coir 40%
Peat 40%
Sand 20%
15.5b
6.53a
3.48b
Coir V/Peat
Coir 40%
Peat 40%
Sand 20%
17.3ab
5.30a
3.75ab
Peat
Peat 25%
Sand 25%
14.2b
5.34b
4.01a
Peat 25%
10.5c
7.06a
2.95c
Pine bark 25%
Perlite 25%
Sand 25%
_____________________________________________________________________________
Peat/Pine bark
Key: Bark=aged pine bark, AFP=Air Filled Porosity, coir V=Vietnamese sourced coir, coir S =Sri Lanka sourced
coir, peat=sphagnum peat, pine fines.
Note: values in the same column with the same superscript are not significantly different (P=0.05).
Table 5.2 Nitrogen draw down of organic components
__________________________________________________
Organic matter source
Nitrate draw down (ppm/day)
__________________________________________________
Coir S
35.2b
Coir V
27.5c
Pine bark
41.0a
Peat
42.5a
__________________________________________________
Note: values in the same column with the same superscript are not significantly different (P=0.05).
Key as above.
29
5.3
The effect of growing medium on flower production of a range
of species
5.3.1 Materials and methods
Species/varieties grown:
1 Anigozanthos cv ‘Spark’
2 Anigozanthos cv ‘Inferno’
3 Anigozanthos cv ‘Tango’
4 Anigozanthos cv ‘Gold’
5 Actinotus helianthi cv ‘C1’
6 Macropidia cv ‘Eclipse’
Plants were transplanted into 10 litre black plastic grow bags on 1 May 2006 and grown under a
plastic rain-shelter until 20 March 2007. Plants were irrigated as required with two trickle outlets in
each container to spread the water through the container and avoid wetting the foliage and flowers.
Flowers were harvested three times a week and the number recorded. There were ten replicates per
variety/growing medium, except for Actinotus which had fifty. Flower number was analysed using a
completely randomised ANOVA design.
Five growing media were used and their components are listed in Table 5.3. All were adjusted to a pH
of 5.5 with a 1:1 mixture of agricultural lime and dolomite. The same additional fertilisers and media
treatment were used as in section 5.2.
The Air Filled Porosity of the media was also determined as in section 5.2. Price of media components
was that paid at April 2006 and the price of media takes into account shrinkage of volume when
components are combined and cost of fertilisers. Cost of mixing media or steam treatment was not
included.
5.3.2 Results and discussion
This trial demonstrated that growth and flowering of the test plants is not necessarily related to the
cost of growing medium. For example, Actinotus produced as many flowers in the lower cost media as
the most expensive (coir/perlite). Overall, for all varieties the coir/sand performed as well as the two
most expensive media: coir/perlite and peat/pine bark. If only Actinotus is to be grown, the pine bark
medium is the most economical.
Counter to the experiment in section 5.2, Actinotus performed equally in all the media. The containers
were much larger and deeper in this experiment which would have greatly improved aeration in the
growing media by providing a greater column depth. Plants were also grown for a much longer time
period and at a lower temperature in the unheated rain-shelter, which would have also affected the
performance of the media and nutrient release rates of the slow-release fertilisers. These experiments
demonstrate the need to trial growing medium under proposed conditions before a standard mix is
adopted or a change made to existing growing medium. The results suggest that substantial savings in
media costs can be made with little or no effect on growth rates.
30
Table 5.3 Air Filled Porosity of growing media and the effect of media on the number of flowers
of different flower species/varieties
___________________________________________________________________________
Major Components
Cost AFP*
No. Flowers/10 litre pot per variety
Name
Components
$/m3
%
Spark Inferno Tango
Gold Actinotus
----------------------------------------------------------------------------------------------------------------Coir/Perlite
Coir 40%
210 10.7a 31.2a 57.6a
16.3a
17.2a
35.4 a
Perlite 40%
Sand 20%
Coir/sand
Coir 80%
Sand 20%
109
11.9a
29.7a
57.1a
15.4a
18.0a
45.9a
Peat/Pine bark
Peat 25%
Pine bark 25%
Perlite 25%
Sand 25%
196
7.4b
31.2a
55.5a
16.3a
15.7a
33.2a
Pine bark
Sand (20%)
Pine bark (80%)
83
11.9a
23.5b
30.0 b
15.6a
13.2a
41.7a
Pine bark/Coir Pine bark 60%
102 10.4a 24.15b 34.5b
16.0a
15.4a
43.3a
Coir 20%
Sand 20%
___________________________________________________________________________
*AFP=Air Filled Porosity
Note: values in the same column with the same superscript are not significantly different (P=0.05).
5.3.3 Conclusions
This experiment demonstrates the need to trial growing medium under planned conditions with the
proposed crops. Even closely related crops may perform very differently in different media and
growing conditions. Substantial cost saving in growing media can be made by substituting lower cost
components for particular crops.
31
6. Use of Gibberellic Acid (GA) to Increase
Flower Stem Length
6.1
Introduction
The market return for Actinotus flowers is directly related to their stem length. Increasing stem length
therefore has the potential to improve market price (Worrall et al.2004). The plant hormone gibberellic
acid (GA) is known to increase the length of stems, along with other effects, in many plants
(Yamaguchi 2008). Application of GA therefore provides a possible mechanism for increasing stem
length in Actinotus.
The aim of this experiment is to determine the effect of GA on Actinotus, especially in relation to
flower stem length.
6.2
Materials and methods
GA (as GA3 and GA4, ProGib®, Abbott Australasia) was applied to Actinotus growing in 10 litre
containers with a standard potting medium composed of equal proportions (by volume) of composted
pine bark fines, sphagnum peat, perlite and coarse sand. Coated potassium sulphate was added at the
rate of 1.5 g/l, Micromax ® trace element supplement at the rate of 0.5 g/l and the pH was adjusted to
6.0 with the addition of dolomite. All plants had just commenced flowering with at least one flower
bud visible, (no mature flowers) and were grown in a heated and cooled greenhouse (13 oC to 25oC)
with 50% shading.
GA was applied at 0, 5, 10, 20 and 40 ppm as a spray (to runoff) on the plants. Flowers were harvested
twice a week for fourteen weeks when they were considered ready to market. Plant height (flowers
and foliage) was measured at the end of the trial to determine the effect of GA on stem elongation.
There were ten replicates per treatment in a completely randomised design.
6.3
Results and discussion
Application of GA had a highly significant effect on stem length. The statistical analysis as an
ANOVA is shown in Table 5.1.
Table 6.1 Statistical analysis of stem length
Source of Variation
ss
df
ms
F
P-value
F crit
Between groups
4168.5
4
1042.13
10.3239
5.1E-06
2.57873
Within groups
4542.4
45
100.94
Total
8710.9
49
Key: df = degrees of freedom, ss = sum of squares, ms = mean square, F pr. = probability of the F value.
As the concentration of GA increased, stem length first increased then decreased (Figures 5.1 and 5.2).
The optimal level of GA was approximately 20 ppm.
32
100
90
Plant height (cm)
80
70
60
50
Y=46.01+2.27X-0.0522X2
R2=0.41
40
30
20
10
0
0
5
10
15
30
20
25
GA (ppm)
35
40
45
Figure 6.1 The effect of GA on plant height. Fitted equation and its regression coefficient (R2)
are shown on the graph.
Figure 6.2 The effect of GA on stem length.
Flowering stem on the left was treated with 20 ppm
GA, plant on the right received no GA
33
Application of GA had no significant effect on the number of flowers harvested (Table 6.2).
Table 6.2 Statistical analysis for number of flowers harvested.
Source of
Variation
ss
df
ms
F
P-value
F crit
Between Groups
228.68
4
57.17
1.056356
0.389124
2.578739
Within Groups
2435.4
45
54.12
Total
2664.08
49
Key: df = degrees of freedom, ss = sum of squares, ms = mean square, F pr. = probability of the F value.
The average length of stems was increased without loss of numbers when up to 20 ppm GA was
applied. Application of GA appears to offer a promising method of improving economic returns. To
maximise returns, dose and time responses still need to be determined for long-term treatment of
plants.
34
7. Propagation of Actinotus and Varietal
Performance
7.1
Seedling material
This project has been based on selected seedling material (see Figures 7.1 and 7.2). Actinotus seed has
a reputation as being difficult to germinate, which was also initially the case with material trialled in
this project. But one line of seed (C1) collected from the wild (from approximately fifty lines
collected) was found to have a viability of 90% with a germination rate of over 80% within six weeks
of sowing. The selected variety (C1) also flowered almost continuously when grown in protected
cultivation and was found to be relatively hardy.
The seed-propagated material also performed exceptionally well, producing over six hundred flowers
per square metre per year. Excellent prices have been received on both the domestic and export
markets making it a very profitable crop. Losses have also generally been low (<5% per year) except
in crops for two growers who withdrew from the project (replaced with other growers). Their high
losses were due to pathogens in the (untreated) irrigation water and inappropriate growing methods.
Plants propagated by cuttings from this material have been trialled but have a much lower growth rate
than the seedlings.
Figure 7.1 High germination rate of
Actinotus seed in trays has enabled
commercial production from seed
Figure 7.2 Following germination, seed is
transplanted to seedling trays that are then
transplanted into growing containers
The major disadvantage of seedling material is its variability; however, propagules are about one-third
the cost of equivalent tissue-cultured material. The variety C1 has been successfully introduced into
culture and multiplied using a standard medium (Figures 7.3 and 7.4). It has proven to be very difficult
to deflask, with large losses occurring or poor growth rates in those that were successful.
There is potential for further selections to be made within the seedling population, especially for
increased vigour and flower stem length, but immediate future production will rely on the existing
seed line.
35
Figure 7.3 Tissue culture of clone C1 in
the laboratory
Figure 7.4 Commercial production of C1 in
a greenhouse
7.2
Other flannel flower hybrids
Mount Annan Botanic Gardens provided six hundred plants in culture of four untested selections for
trial that were deflasked by the University of Queensland in Gatton. These plants were then trialled at
both Gosford and in a number of grower’s rain-shelters. Some plants failed to flower and others only
produced a limited number of flowers (Figure 7.5) – none of the tested clones were considered
economically viable for cut flower production.
Figure 7.5 Few flowers were produced by
some of the selected clones of Actinotus
36
8. Post-Harvest Characteristics of
Actinotus
8.1
Introduction
Flannel flower vase life can vary from less than seven to thirty-five days (Faragher et al. 2002).
Although average vase life is around 10–14 days, this can be considerably shortened by cold storage
during transport and resale. Even if flowers appear acceptable, buds fail to develop properly and open
post-harvest.
General recommendations by Faragher et al.. (2002) are often followed in commercial practice as they
work well; Figure 8.1 indicates best practice harvest and storage methods. Nevertheless, increased
storability and improved flower development during vase life would improve marketing flexibility and
ensure customer satisfaction.
(a)
(b)
(c)
(d)
Figure 8.1 Normal post-harvest handling practices for Actinotus grown in protected cultivation
(a) Harvested flowers are placed immediately in water or a hydrating solution and held in a
o
coolroom at about 4 C. (b) Flowers are dipped in a fungicide and insecticide solution then
sleeved for protection with either foiled backed (shown here) or plain micro-punched plastic.
(c) Failure to treat flowers with a post-harvest fungicide and insecticide dip may result in
Botrytis infestation (shown here) and/or live insects in the flowers. (d) Bunches are then
packed into boxes with a plastic liner and are offset to enable greater packing densities.
37
A variety of cut flowers respond reasonably well to a range of chemicals added to the vase solution but
there appears to be no published experimental results specifically for Actinotus flowers.
HQS (8-hydroxyquinoline citrate) has been shown to increase the vase life of a wide range of cut
flowers by inhibiting stem blockage (through both physiological action and anti-microbial effects) as
well as causing stomatal closure (that reduces water loss). Silver thiosulphate (STS) is used
commercially to inhibit ethylene production and reduce the flower’s sensitivity to ethylene (Jones and
Moody 1993, Faragher et al. 2002), preventing petal drop and premature senescence. It may also
prevent stem blockage due to its anti-microbial properties.
Addition of carbohydrates such as sucrose to the solution may also increase vase life (Faragher et al..
2002) but would need an anti-microbial agent added to prevent the growth of microorganisms in the
vase solution.
Figure 8.2 Normal harvest stage for Actinotus cv C1 inflorescences
The purpose of this trial is to determine if a range of common vase solutions could be used to extend
the vase life of Actinotus flowers.
8.2
Materials and methods
Actinotus flowers (variety ‘C1’) were harvested from plants growing in a rain-shelter. Figure 8.2
shows a flower at the normal harvest stage. All inflorescences had one flower with the bracts fully
reflexed. Flowers were placed individually in 25 mm wide by 125 mm deep tubes with the range of
preservative solutions shown in Figure 8.3. The solutions were changed daily. The flowers were held
under standardised environmental conditions (Sytsema 1975) to determine vase life. End of vase life
was deemed as wilting of the inflorescence. There were thirty replicates per treatment and statistical
analysis was undertaken as a randomised ANOVA.
38
Vase life (days)
20
18
16
14
12
10
8
6
4
2
0
Control
Ag
Ag & 1%
sugar
HQS
HQS & 1%
sugar
lsd 5%
Vase solutions
Figure 8.3 The effect of preservative solutions on vase life
Key: Control=distilled water; Ag=pulsed for 16 hours with 2 mM Ag ions as sodium thiosulphate and silver
nitrate then distilled water; Ag & 1% sugar=pulsed for 16 hours with 2 mM Ag ions as sodium thiosulphate and
silver nitrate plus 1% w/w sucrose then 1% w/w sucrose; HQS=2 µM 8-hydroxyquinoline citrate (50 ppm w/w);
HQS & 1% sugar=2 uM 8- hydroxyquinoline sulphate plus 1% w/w sucrose; lsd 5% = least significant
difference at the 5% probability level.
8.3
Results and discussion
No preservative vase solution increased the vase life over the control. In fact, the vase life of flannel
flowers was significantly (P<0.05) reduced by the addition of silver ions. Silver ions usually extend
the vase life of flowers by inhibiting the action of ethylene. In the case of Actinotus, this pulsing
solution was actually toxic, reducing vase life. It seems likely that Actinotus flowers are not sensitive
to ethylene, although this needs to be confirmed by further experimentation.
Sucrose, at the rate tested, also did not improve the flowers vase life. This rate is suggested by
Faragher et al..(2002) as being suitable for extending the vase life of a wide range of Australian native
cut flowers but flannel flowers appear unresponsive.
From this trial there is no evidence that commonly used preservative solutions or sucrose will extend
the vase life of Actinotus cut flowers. Flannel flowers grown under protected cultivation and handled
correctly have a commercially acceptable vase life without the use of floral preservatives. However, it
is also noted that anti-bacterial agents (such as chlorine) in the holding or vase solution can reduce
microbiological contamination.
8.4
Conclusions
There is no evidence that Actinotus flowers are particularly sensitive to ethylene or that the addition of
sucrose to the vase solution improves vase life. The vase life of flowers grown under protected
cultivation is currently commercially acceptable so further experimentation would be of little
economic value at this time.
39
9. Discussion and Key Findings
The key impediments to cultivation of flannel flowers in developing a commercially viable production
system were overcome:
1 Control of root diseases especially with improvement of growing medium aeration
2 Development of high yielding, elite all-year-round flowering with a long post-harvest life
3 Increased stem length using growth regulators
4 Improving cultural practices
5 Improving propagation efficiency
6 Trialling of new crops to identify those with commercial potential.
The major focus of this project has been on the development of flannel flowers as a cut flower crop
under protected cultivation. To date, over thirty thousand plants have been distributed to growers for
trialling. Three-quarters of the plants were grown from seed, the remainder being from cuttings of one
clone. The parent material of both the cuttings and seedlings has flowered all-year-round and the
seedling material has been continuous. Commercial co-operators have also produced large quantities
of seedlings and as a result of this project. Fifteen growers are now producing flannel flower as a cut
flower crop in protected cultivation. Additionally, this work has provided an opportunity to expand the
industry by introducing new crops in protected cultivation.
Flannel flower in protected cultivation is a potentially profitable new product for the Australian native
cut flower industry now that impediments to cultivation and propagation have been overcome. Other
products also show this potential. Furthermore, a shift to protected cultivation will assist in curtailing
environmentally harmful practices associated with bush-picking.
40
10. Recommendations
Although this project has achieved a commercially viable outcome, continued development is
necessary in maintaining the competitive advantage of the industry. These issues can be broadly
grouped as cultural requirements, propagation, breeding and marketing. These issues would benefit
by:
1
Conducting fertiliser and watering studies to further optimise growth rates.
2
Running trials to further define optimal environmental conditions especially with respect to
growing conditions (e.g. heat, light, humidity).
3
Improving tissue culture methods to enable the use of clonal materials for flower production.
4
Continuing seedling line developments through plant selection to further improve flower
numbers and quality.
5
Identifying the breeding systems of Actinotus and exploring the use of other species such as
A. schwarzii in a breeding program.
6
Encouraging private industry to develop their own cultivars of Actinotus and other species for
commercial flower production.
41
Appendix 1
Growing flannel flowers for the cut flower market – A guide for
commercial growers
This guide will be provided as an appended volume to this publication and includes the findings of this
project as well as other information with the aim of providing a complete guide (as complete as
possible) for the production of Actinotus flowers in the greenhouse. The guide will become available
in late 2010.
42
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44
Growing Flannel Flowers all Year Round
by By Dr Ross Worrall and Len Tesoriero
Publication No. 10/065
There is a well-established domestic and export market for cut
flannel flowers (Actinotus helianthi) with out-of-season flowers
command a significant premium. Demand already exceeds
supply, which will be exacerbated in the future with proposed
actions to severely reduce bush picking.
RIRDC is a partnership between government and industry
to invest in R&D for more productive and sustainable rural
industries. We invest in new and emerging rural industries, a
suite of established rural industries and national rural issues.
Most of the information we produce can be downloaded for free
To date, Actinotus sp. has proven unreliable in cultivation as it is or purchased from our website <www.rirdc.gov.au>.
difficult to propagate and has a short flowering season limited
RIRDC books can also be purchased by phoning
to spring and early summer. In response, the Flannel Flower
1300 634 313 for a local call fee.
Forum has identified the major constraints limiting cultivation
– in particular the lack of suitable varieties, cultural information,
propagation and the effect of root diseases. Overcoming these
production constraints will provide business and employment
opportunities for regional Australia.
Most RIRDC publications can be viewed and purchased at
our website:
www.rirdc.gov.au
Contact RIRDC:
Level 2
15 National Circuit
Barton ACT 2600
PO Box 4776
Kingston ACT 2604
RIRDC
Ph: 02 6271 4100
Fax: 02 6271 4199
Email: [email protected]
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