Performance of Everbearing Strawberry Cultivars in a Nordic Climate
A. Nes and A. Sønsteby
Arable Crops Division
Norwegian Institute for Agricultural and
Environmental Research, Nes Hedmark
Norway
O.M. Heide
Department of Ecology and Natural
Resource Management
Norwegian University of Life Sciences, Ås
Norway
Keywords: cultivars, everbearing, Fragaria × ananassa, strawberry, yield
Abstract
In the Nordic strawberry industry only single-cropping cultivars are used.
Several everbearing cultivars have been tried, but neither yield nor quality has been
satisfactory. In 2005, new everbearing cultivars were collected and an experiment
was established in a polyethylene tunnel. Yield and runnering capacity were
recorded in two seasons. The cultivars were the English ‘Flamenco’ and ‘Everest’,
the Dutch ‘Elan’ and the Norwegian ‘Rita’, ‘Rondo’, ‘Ridder’ and ‘Rosa’. Plug
plants were planted in double rows on low ridges mulched with plastic at a plant
density equivalent to 50,000 plants per ha. A block design with 20 plants per plot
and four replicates was used. The field was harvested two to three times a week
during the whole season from June until the beginning of October in both years.
Berry size was recorded at all harvests while taste and general performance were
evaluated using a scale 1-9. In the first year, the everbearing cultivars had
significantly higher yield than the single-cropping cultivars due to more
inflorescences, but this was levelled out the second year. While the cropping season
of the single-cropping cultivars is only about four weeks, the everbearing cultivars
were picked from late June until beginning of October, in both years. The highest
yields were obtained by ‘Everest’ (729 and 844 g) followed by ‘Rita’ and ‘Ridder’.
The cultivars ‘Elan’ and ‘Rondo’ scored highest both in taste and general
performance. ‘Everest’ also performed well, but flavour was not acceptable.
INTRODUCTION
During the years, many single-cropping and some everbearing cultivars from
different breeding programs have been tested in the Nordic climate in Norway (Nes,
1997). While several single-cropping cultivars have been accepted because of good yield
of high quality, no everbearing types have been accepted. The strawberry season in
Norway begins in mid-June (at about 58°N), and ends about mid-August (at about 63°N).
Most of the strawberry production is, however, largely concentrated in the South-Eastern
part of the country, giving a short season of only 3-4 weeks in this period, too many berries
are over-flooding the marked, and the prices are low. To avoid this there is an increasing
interest of alternative production methods to stretch the season. Different strategies have
been tried: waiting bed plants or to utilise the effects of different preconditioning treatments
in the main cultivar ‘Korona’ (Sønsteby et al., 2006; Nes et al., 2002). Use of everbearing
cultivars is another alternative. The paper presents results from an investigation where some
new everbearing cultivars have been tried in our climate.
MATERIAL AND METHODS
The cultivars ‘Flamenco’ and ‘Everest’ from England, the Dutch ‘Elan’ and the
Norwegian ‘Rita’, ‘Rondo’, ‘Ridder’ and ‘Rosa’ were collected and an experimental field
was established in a polyethylene tunnel at Bioforsk Øst Kise (60°40’N, 10°11’E) in the
South-Eastern part of Norway in autumn 2005. Plug plants were planted in double rows
on low ridges mulched with plastic at a plant density equivalent to 50,000 plants per ha. A
block design with 20 plants per plot and four replicates was used. The experimental field
was fitted with a pressure compensated trickle irrigating system with an emitter spacing
of 50 cm and a capacity of 1.6 L/h. Fertigation was carried out twice a week during most
Proc. VIth Internat. Strawberry Symposium
Ed.: J. López-Medina
Acta Hort. 842, ISHS 2009
781
of the growing season. Predators were used to control pests like spider mite (Tetranychus
urticae) and thrips (Thysanoptera spp.). Because of heavy attack of different pests, all
plants of the cultivars ‘Rita’ and ‘Rosa’ were removed in week 34 the second year. The
plots were harvested two to three times a week during the whole season from June until
beginning of October in the years 2006 and 2007. Yield, berry size and discarded berries
were recorded at all harvests while taste and general performance were evaluated three
times early in the season using a scale 1-9 (not shown). Data of outside temperature are
collected from the official meteorological station close to the experimental field (Table 1).
RESULTS AND DISCUSSION
The observations presented in Table 1 show that the temperatures were very high
compared to the 30 year normal (1960-1990) in both years, with an extraordinary warm
July and August the first year. Early in the season the temperatures were higher in the
second year than the year before. Average temperatures were well above normal during
the growing season in both years.
Yield
With the exception of ‘Everest’, all cultivars yielded less the second year (Table
2). On average for the seven cultivars the crop was reduced by more than 25% the second
year. This is in contradiction to single-cropping cultivars that in a similar experiment
(data not shown) gave more than 500% yield the second year. ‘Everest’ had the highest
yield both years, followed closely by ‘Rita’ the first year. The latter had, however, only
half crop the second year. The yield of ‘Rosa’ was even more reduced the second year.
Besides ‘Everest’ the cultivars ‘Elan’, ‘Ridder’ and ‘Rondo’ also had acceptable yield the
second year.
Berry Size and Grading
According to The Norwegian Standard only berries with diameter above 25 mm
are saleable on the fresh marked. In this experiment ‘Rita’ had significantly smallest
berries and only 30-40% of the total yield could be sold (Table 2). The cultivars ‘Everest’,
‘Flamenco’ and ‘Rondo’ gave biggest berries, but the berry size of ‘Everest’ was
significantly reduced the second year. The cultivar ‘Rondo’ had biggest berries in average
of both years and 40% of the crop of this cultivar had berries with a diameter above
30 mm.
Discarded Berries
There were most discarded berries the first year. There is no obvious explanation
for that, but some attack of both strawberry mildew (Sphaerotheca macularis) and thrips
(Thysanoptera spp.) occurred in the periods with very high temperatures in July and
August the first year and this could have had an affect. The fact that the cultivars ‘Rita’
and ‘Rondo’ were removed from the field in week 34 also had an influence. Significant
differences in resistance between the seven cultivars are demonstrated.
Harvesting Season
In the first year the cultivars gave the first ripe berries the last week of June –
some already the week before (Fig. 1). In the second year the temperatures in May and
June were higher and the season began about one week earlier. Both years the yield
showed a peak in the second and third week followed by very little yield the next three to
four weeks when yield reached a second peak. In the first year the second peak was
earlier than in the second year. The temperatures in July and August were much higher
the first year making the time from flower induction to harvest shorter. The cultivar ‘Rita’
showed a little different pattern giving a very high early yield in both years but less late in
the season when the berry size was very small. The harvesting season in single-cropping
cultivars lasts 3-4 weeks but all cultivars in this experiment were picked for a period of
15-17 weeks. Everbearing strawberry cultivars are long-day plants at intermediate and
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high temperatures, but day-neutral at low temperatures (Sønsteby and Heide, 2007).
Therefore, flowers for the early crop peak must have been induced in the autumn the year
before, while the late crop peak came from flowers induced and differentiated in the
current year.
CONCLUSIONS
Only a few of the tested everbearing cultivars will be included in further trials.
‘Everest’ was healthy and high yielding but flavour was not acceptable. The cultivars
‘Elan’ and ‘Rondo’ had an acceptable yield and scored highest both in taste and general
performance. But mildew may be a problem in ‘Rondo’. The other cultivars were found
not acceptable.
Literature Cited
Nes, A. 1997. Evaluation of strawberry cultivars in Norway. Acta Hort. 439:275-280.
Nes, A., Grimstad, S.O., Opstad, N., Hageberg, B. and Hagelund, R. 2002. Stategies of
raising transplants for strawberry production in a prolonged season in a Nordic climate.
Acta Hort. 567:281-284.
Sønsteby, A., Heide, O.M., Grimsby, I. and Grimsby, S. 2006. Out-of-season strawberry
production in Norway: Yield responses of cv. Korona to photoperiod preconditioning
treatment. Acta Hort. 708:371-374.
Sønsteby, A. and Heide, O.M. 2007. Long-day control of flowering in everbearing
strawberries. J. Hort. Sci. Biotech. 82:875-884.
Tables
Table 1. Outside mean temperature in the growing season of the two experimental years
compared to normal at the meteorological station Kise, Hedmark.
2006
2007
Normal
May
9.1
9.7
8.5
June
14.4
15.1
13.6
July
18.5
15.5
15.2
August September October May-October
17.0
13.6
7.3
13.3
15.2
15.7
5.7
12.8
14.0
9.6
5.1
11.0
Table 2. Yield (g/plant), grading (%), berry size (g/berry) and discarded berries (%) of
seven everbearing strawberry cultivars in two years.
Cultivars
Everest
Flamenco
Ritax
Rondo
Ridder
Rosax
Elan
X
Yield
2006
729
563
709
547
639
663
635
2007
844
491
337
388
574
149
542
Grading in berry diameter
<25 mm
25-30 mm
>30 mm
2006 2007 2006 2007 2006 2007
25
26
32
45
43
29
30
29
36
35
35
36
61
75
28
22
11
3
29
27
31
33
40
40
32
33
31
32
37
34
39
45
33
34
28
21
42
34
33
38
25
28
Berry size
Discarded
berries
2006 2007 2006 2007
12.0 8.6
3.6 2.4
10.3 10.0
9.0 6.4
6.0 5.0
10.2 1.7
12.0 11.1
8.4 4.9
9.5 10.2
3.8 2.8
8.5 7.2
13.5 8.9
9.1 9.0
4.8 3.1
only 24 out of harvests in 2007.
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Figures
150
2006
-1
Yield (g plant )
125
100
75
50
25
-1
Yield (g plant )
0
150 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
2007
Time (week no.)
125
Everest
Flamenco
Rita
100
Rondo
Ridder
Rosa
75
Elan
50
25
0
25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
Time (week no.)
Fig. 1. Yield (g/plant/week) of seven everbearing cultivars in two years.
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