Disphyma australe at Bethels Beach, Auckland
“Cliffs are places to find
plants suitable for greenroofs”
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Lava flows and rock rubble also support
possible greenroof plants ‘the scoria boulders
in Mount Wellington crater support native
bidibid, Acaena microphylla
potential nz native plants for
extensive greenroofs
Greenroof plants must have high tolerance of drought
by having low moisture requirements, not extensive
root systems or bulky root storage organs – extensive
greenroofs usually have 50 to 150 mm deep mm
substrates with available water capacity of only 6 to 18
mm (2 to 5 days water supply in summer for pasture).
Features of drought-tolerant plants include very small
leaves (Coprosma acerosa and Carmichaelia) or thick,
succulent leaves with waxy cuticles as (Disphyma
australe), or the specialized photosynthetic cycle found
in the Crassulaceae which enables them to close their
stomata during daylight hours, thus reducing moisture
loss. Orchids, e.g., Microtis and Thelymitra longifolia, and
Lycopodiums have been excluded, as have mosses and
lichens – the bryophytes have been reported as being
particularly susceptible to damage by foraging and nestbuilding birds. Images of many of the plants are on the
New Zealand Plant Conservation Network website
(www.nzpcn.org.nz).
This document lists native groundcovers, grasses and
ferns, in alphabetical order, that could be used on
extensive greenroofs. The plants are mainly sourced
from a list of NZ plants identified by Colin Meurk as
suitable for dry lawns and rock gardens with growth
forms up to 150 mm tall. It includes some additional
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plants from a related ‘rock garden’ list, and observations
of plants in rocky, exposed environments (e.g., old
stone walls) as suggested by Mark Smale and Colin
Meurk. The list is not exclusive or exhaustive. It list
includes many species that are not readily available
from nurseries, however, the plants that a bolded are
being trialed on two extensive greenroofs in Auckland
on substrates ranging from 50 to 125 mm depth, and
most of these plants are readily available from native
plant nurseries. A list of the native species on each roof,
photo, and indicative results after the first year of the
trials is included. In 2008 the performance of a wider
range of native plants and some exotic species, will be
trialed on substrate depths up to 150 mm, allowing us
to recommend specific plants suited to the Auckland
environment.
Note that within species there are growth forms and
varieties of plants that are better adapted to greenroofs,
for example, Selliera radicans varies greatly in leaf size and
shape depending on source; Coprosma acerosa varies from
a fairly open upright form which can be susceptible to
collar-rock on greenroofs, to a more successful, extremely
prostrate form with shorter internodes. This list does not
include plant varieties or cultivars that may be suitable
for greenroofs, e.g. Coprosmas and Libertias.
Old rock walls support likely greenroof plants’ - This dry-stone
wall of scoria in Cornwall Park, Auckland has been colonised
by the leathery fern Pyrossia serpens, and native succulent
Crassula sieberiana.
3
Bidibid - Acaena microphylla ‘purpurea’
Everlasting flower - Anaphalioides bellidioides
4
1. Potential groundcovers for New Zealand greenroofs
Species
Height (mm)
Natural habitat
Flowers & ecological services
Acaena microphylla
Bidibid or scarlet piripiri
50 to 100
Grassland and river
terrace, gravelly
riverbeds*1
Rhizomatous mat-forming
perennial. Attractive, massed
red-pink ‘spiky’ fruit in summer
(Nov-Jan)
Anaphalioides bellidioides2
Everlasting flower
50
Grassland and open
shrubland, lowland to
montane
Main stems prostrate and rooting
White conspicuous daisy in
summer
Calysteia soldanella
Sand convolvulus or
shore bindweed
100 to 150
Coastal sandy habitats
behind beaches (dunes)
Perennial ground vine with
creeping rhizome. Large pale
pink to mauve flowers in spring
to summer (Oct to March)
provide necta
Coprosma acerosa
300
Coastal sands and rocks
throughout NZ
Shrub with interlacing branches
forming a cushion up to 2 m
diameter. Pale blue berries c.
7mm diameter. Will hang.
Coprosma petriei
100
Short turf grasslands;
stream margins, rocky
places
Sub-shrub with creeping and
rooting branches forming dense
mats up to 2 m diameter. Red to
pale blue fruit, 6-8 mm diameter
Crassula sieberiana
10
Rocks, cliffs and coastal
open ground
Yellowy-green herb forming
dense patches rooting along the
ground. Insignificant flowers
(Aug to Dec)
Cyathodes fraseri
Leucopogon
50 to 150
Coastal dunes, rocks,
open grassland, frostflats
Prostrate to low growing shrub
forming dense patches, 8 to 9
mm long orange to yellow fruit
Dichondra repens
Mercury bay weed
10 to 20
Short turf, coastal cliffs
& ledges to montane
forest clearings
Prostrate herb forming creeping
mats to 2 m
Disphyma australe
NZ ice plant
100
Coastal banks, rocks
and cliffs
Trailing open herb with large
(20 to 60 mm diameter) white
to deep pink to mauve flowers in
early summer (Oct to Jan)
Elymus solandri
200
Coastal cliffs, inland
grasslands and riverbeds
to 1500 m
Open grass rooting and shooting
at nodes with blue-grey foliage
1 Var. pauciglochidiata is found on coastal gravels and sands.
2 Formerly known as Helichrysum bellidioides
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NZ daphne – Pimelea prostrata
Species
Height (mm)
Natural habitat
Flowers & ecological services
Fuchsia procumbens
100
Sandy, gravelly or rocky
places and beaches
Creeping shrub with 12 to
20 mm long tubular nectarproducing flowers in summer
and large oblong (20 mm) pink
to bright red berries.
Leptostigma setulosa3
50 to 100
Short turf, open scrub,
frost flats
Pale green leaves create
slight mounds. Red fruit
inconspicuous.
Libertia peregrinans*
NZ iris
300 to 400
Sandy, peaty and pumice
soils from sea level to
1000 m
Fans emerging from spreading
rhizomes, copper colour in full
sun, White c. 20 mm diameter
flowers on short spikes and
brown capsules with orange fruit
Muehlenbeckia axillaris4
Creeping pohuehue
150
Coast sands to riverbeds
and open rocky places
Interlacing branches forming
tangled insect habitat, small
white flowers in summer, fleshy
opaque fruits
Pimelea prostrata5
NZ daphne, pinatoro
100 to 150
Coastal to subalpine
gravels, riverbeds terraces,
open shrubland
Prostrate to sprawling shrub
with grey foliage and small white
flowers and berries (2mm) spring
to autumn
Peperomia urvilleana
Wharanui
150
Coastal rocky places &
forest, often epiphytic
Slowly spreading succulent herb.
Nil
Samolus repens
Maakoako
150
Damp saltmarsh and
rocky places
Perennial herb with prostrate
branches rooting at nodes. White
6 to 7 mm long white flowers in
spring
Scirpus nodosus6
Leafless sedge
300
Sand dunes and from sea
level to 600m
Brown composite fruit
Scleranthus biflorus
50 to 100
Coastal rocks and
grassland
Perennial close-branched herb
forming relatively loose, bright
green mounds Nil
Selliera radicans
50
Coastal mud, sands and
rocky places; inland
stream margins to 1000 m
Herb with long creeping stems
rooting at nodes forming mats up to
5 m diameter. Small (7 to 10 mm)
white to pale blue scented flowers.
Wide range in form and size.
3 Formerly Nertera, probably better suited to areas with some shade
4 NZ Flora notes “a complicated aggregate of forms is included under the name M. complexa”. It is probable that hybridism is one reason for this variety of forms, for example botanists have noted hybrids of M. complexa
with M. axillaris, M. australis and M. ephredioides.
5 NZ Flora notes a great complex of forms, including some that are genotypic (breed true to form) but others that are habitat modifications, with evidence of hydrids with other species.
6 Fomerly Isolepis nodosa and Holoschoenus nodosus
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Leptostigma setulosa
7
Other potential groundcover species
• Brachyglottis bellidioides7
• Lagnifera species, L. pumila is probably the most
drought resistant
• Carmichaelia corrugate & C. uniflora, prostrate
brooms, nitrogen fixing shrubs
• Raoulia, cushion plants
• Colobanthus species, about 8 species, see www.
nzpcn.org.nz
• Stackhousia minima, tiny herb with outsized tubular
red flowers – maybe too small
• Coprosma atropurpurea, very low spreading cushion
• Wahlenbergia albomarginata, New Zealand bluebell
• Epilobium species, New Zealand willowherbs,
comprising 37 species difficult to tell apart
and tend to hydridise so may impact local
populations?). Some willowherbs resemble
sedums, e.g., E. pycnostachyum
• Geranium, 6 native species
• Gonocarpus aggregatus
• Haloragis depressa
• Helichrysum filicaule, everlasting daisy
• Lepidium species
• Leptinella serrulata
• Leucopogon fraseri
• Luzula celata, woodrush
• Mazus pumilo, probably for shadier areas
• Muehlenbeckia ephredroides, threatened prostrate vine
• Neopaxia australasica, montia, shadier areas
7 Also known as Senecio bellidioides
Mazus pumilo
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“Flowers attract bees!”
Selliera radicans
2. Potential grasses and monocots for New Zealand greenroofs
• Austrofestuca littoralis (sand tussock)
• Microlaena stipoides (Auckland)
• Agrostis species (NZ bentgrass)
• Poa imbecilla, P. lindsayi, P. maniototo
• Carex resectans, sedge
• Pyrrhanthera exigua (mountain twitch)
• Festuca actae, F. coxii
• Rytidosperma species
• Lachnagrostis species, e.g., Lachnogrostis filiformis/
billardierei
• Zoysia minima (sand twitch or prickly couch)
Rock wall with Pyrrosia eleagnifolia,
lichens and Crassula sieberiana
Festuca coxii
3.Potential ferns for New Zealand greenroofs
• Cheilanthes (growing on soil veneer over rock on
Tiritiri matangi Island)
• Ophioglossum coriaceum (adder’s tongue fern, sand
dune hollows8 )
• Pellaea rotundifolia (chainfern)
• Phymatosoros pustulatus (hounds tongue fern)
• Pleurosoros rutifolius (hot rock fern)
• Psilotum nudum
• Pyrrosia eleagnifolia = P. serpens (ngarara wehi, rock
walls in Auckland)
8 www.sbs.auckland.ac.nz
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case study
NZ Iris – Libertia peregrinans
Sedum alba
University of Auckland, School of Engineering Greenroof Plants
• Acaena microphylla – bidibid
• Coprosma acerosa ‘Hawera’ - a prostrate
variety of sand dune coprosma
• Cotula australis
• Crassula sieberiana - succulent sourced
from scoria rock walls
• Disphyma australe - New Zealand iceplant
• Festuca coxii – a type of tussock grass
• Libertia peregrinans – New Zealand iris
• Mazus pumilo
• Pyrrosia eleagnifolia - sourced from scoria
rock walls, planted in the second winter
• Selliera radicans
The greenroof was constructed in late spring 2006. After
one year Disphyma australe and Crassula sieberiana have
established large numbers of new seedlings across most
of the roof, including areas where they were not originally
planted. Crassula may not provide year-round cover.
We wait to see if the new iceplant seedlings will survive
summer. Vegetation data quantifying performance after
the first year has yet to be analysed, however, species that
have highest survival are iceplant, crassula, fescue, sanddune coprosma and NZ iris. Some individuals of all
plant species survive on the roof – no species has failed
entirely, however, survival appears to be highest on areas
with more shade and deeper substrate (plots are either
50 or 75 mm depth).
Native plant section of Plot one, spring 2007, about one year after establishment, showing Crassula sieberiana (right and background) with iceplant (light green
succulent in foreground), NZ iris (orange spikey foliage on left) and fescue (blue tussock grass in the centre). Two sedum species have invaded the plot (bright
yellow Sedum mexicanum upper left and a variety of Sedum album – the blue succulent within iceplant in centre foreground and left)
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case
study
case
study
Convolvulus – Calystegia saldanella
Selleria with Disphyma
Waitakere Civic Centre Greenroof Plants
About 50% of the plants were the following three species
• Disphyma australe* – New Zealand iceplant
• Coprosma acerosa* – sand dune coprosma (prostrate
and upright forms)
• Libertia peregrinans – New Zealand iris
Smaller proportion:
• Calystegia soldanella* – sand dune convolvulus
• Dichondra repens* – Mercury Bay weed
• Selliera radicans*
• Leptostigma setulosa
• Acaena microphylla – bidibid (green form)
• Pimelea prostrata – New Zealand daphne
• Festuca coxii
• Muelenbeckia axillaris and M. complexa (in an area
with substrate to 200 mm depth)
The greenroof was constructed in winter 2006. After one
year Disphyma australe has established large numbers of
new seedlings. Vegetation data quantifying performance
after the first year has yet to be analysed, however, species
that have highest survival are iceplant, fescue, sand-dune
coprosma and NZ iris. Some individuals of all plant
species survive on the roof, however, the diversity and cover
of plants is highest on areas with deeper substrate (100
to 150 mm depth); two areas with thin substrates (c.70
mm depth) have had moderate to high plant mortality.
Mercury bay weed, Selliera and Leptostigma died back in
summer but have spread dramatically since autumn rains
have fallen – these species may be best suited to deeper
substrates or areas with afternoon shade.
(* = sourced from the Waitakere Ecological District source):
Waitakere greenroof in spring 2007, just over one year after establishment. A 1 to 2 m wide strip of deeper substrate along the left hand side is planted in
Muehlenbeckia species, white-flowering NZ daphne (Pimelia) and rounded mounds of Leptinella. The remainder of the roof is visually dominated by the
tall spikey fescues (blue tussocks) and NZ iris (orange), and lime-green iceplant.
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