The weeds of Garden Island – An annotated list

16 Pages·1998·3.4 MB·

by  Greg Keighery

THE WEEDS OF GARDEN ISLAND -
AN ANNOTATED LIST
By GREG KE1GHERY
Department of Conservation and Land Management
P.O. Box 51, Wanneroo, 6065.
ABSTRACT
Currently 122 species of weed have been recorded fron
Garden Island, the site of the first European settlement on
the West Coast of Western Australia in 1829. The most
serious weed of Garden Island is Arum lily. Another
potentially serious weed is Bridal Creeper. There are 30
widespread weeds (Homeria and Trachyandra could be
serious) on the island. Nine weeds restricted to beaches and
another 6 confined to rocky headlands, including the serious
weeds; Lycium and Lavatera. Eleven weeds recorded for the
island appear to have become extinct and 6 weeds are just
persisting. There are 4 very localised weeds, one Agonis
flexuosa (Peppermint) needs to be removed urgently. There
are 10 weeds localised to developed areas. New weed records
are mainly from the developed areas and beaches and require
monitoring.
INTRODUCTION have been largely cleared and the
Recently there have been remaining remnants severely
published a series of studies on impacted by weeds, feral animals,
the native vegetation, flora fire, and other disturbances, thus
(McArthur, 1990 and Keighery et they are in need of extensive
a1., 1997) and fauna (Brooker et aI., rehabilitation. Garden Island is
1995 and Brooker et al.t 1995) of the key area for the continuance
Garden Island. of these now rare communities
and should be kept as free of
These studies have demonstrated
weeds of these communities as
that Garden Island contains a
possible.
number of very significant plant
communities, especially those Apart from one very serious
woodlands and forests dominated invasive weed, the Arum Lily,
by Callitris preissii or Melaleuca about which a workshop was
lanceolata. Elsewhere, on the recently held (Scott and Wykes,
mainland and Rottnest Island 1997), little is known about the
occurrences of these communities abundance, distribution and
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effects of weeds on Garden Island. since the last published listing
This paper documents major (Marchant and Abbott. 1982) there
changes that have occured in the have been additions, deletions
weed flora over the last 14 years. It and other changes, for example,
also details the current state of our surveys in 1992 revealed 22
knowledge of the other new records of introduced plants
introduced and naturalised for the Island.
plants of Garden Island and uses
comaparable mainland sites and
A) CHANGES
data to estimate threats of these
Four factors affecting the weed
weeds.
flora of the Island have changed
greatly since the last major suvey
in 1979 (Marchant and Abbot,
METHODS
1981).
To compile a list of the weeds of 1) Cessation of uncontrolled
Garden Island all known pub¬ introductions occurring around
lished and unpublished sources the Settlement and northern
and opportunistic collections shacks.
were consulted, with the records
Most of the species grown in these
updated to current taxonomy.
areas listed in previous reports
Quadrats established as part of the
have either:
floristic survey of the Swan
Coastal Plain (Gibson et at, 1994) (a) Apparently died out-This
were used to assess weed spread. A includes the records for the
separate ground survey of the following 6 planted garden
weeds of Garden Island and species: Auricaria heterophylla
Woodmans Point was under¬ (Norfolk Island Pine), Punicea
taken in 1992. Weeds were rated granatum (Pomegranate), Craetagus
on their actual potential impact sp. (Hawthorn), Hedra helix (Ivy),
on the natural communities of Ixora sp.and Vitis vinifera (Grape).
Garden Island by reference to (b) Have persisted, or spread only
Woodmans Point, Rottnest Island marginally by vegetative means-
(Keighery, 1986) and the Perth area This includes the records for the
as detailed in Dixon and Keighery following 15 species: Agave
(1995). americana (Century Plant), Allium
ampeloprasum (Wild Leek),
Eucalyptus gomphocephala (Tuart),
GENERAL NOTES ON THE Euphorbia dendroidea (Tree Spurge),
WEED FLORA OF GARDEN Ficus carica (Fig), Ipornaea indica
ISLAND (Blue Morning Glory), Iris
germanica (German Iris), Leucojeum
The weed flora of Garden Island is
aestivum (Snowflake), M elia
listed in Appendix 1. Currently a
azederach (Cape Lilac), Narcissus
total of 122 taxa of introduced
tazetta (Jonquil), Nerium oleander
plants have been recorded from
(Oleander), Ornithogalium
the Island.
arabicum (Arabs Eye), Schinus
This weed flora is not static and terrebinthifolius (Japanese Pepper)
62
and Vinca major (Vinca). One The single plant of Sea Wheat
species, Anredra cordifolia (Potato probably came from Woodmans
Vine) is apparently still spreading Point, where the species is
via bulbils in the leaf axils. abundant on the fore dunes. If
other plants arrive and establish it
2) Capping of the old bores where
numerous weeds grew and will also become a major
flourished. component of the strand flora.
This has apparently resulted in 4) The presence of irrigated lawns
the demise of 5 previously re¬ and frequent vehicular traffic to
corded species listed: Cymbalaria the mainland is giving a new suite
muralis (Ivy Leaved Toadflax), of weeds at the Stirling Base. A
Nasturtium officinale (Water Cress), notable example of this is Juncus
Musa sapentium (Plaintain acutus (Spiny Rush) which has
Banana), ?Arundo donax (Bamboo) invaded irrigated ovals from a
andTypha orientalis (Bullrush). nearby drainage basin (G1EAC,
1996). Some of these weeds could
3) Increases in the number of
build up populations here and
weeds present on the beaches of
then spread into adjacent
Garden Island- During my brief
bushland areas.
studies on the island 1 have
located 7 new weeds on the One potential weed in this
beaches and headlands of Garden catagory is Hibbertia cueniformis
Island: M esembryanthemum (Cutleaved Hibbertia) which
crystallinum (Ice Plant), Arctotheca Wykes (pers. comm., 1997) has
calendula x populifolia, Conyza noted that planted material is
parva (Fleabane), Euphorbia paralias self-seeding around the base.
(Sea Spurge), Thinopyrum distichus Elliot and Jones (1990) have
(Sea wheat) and L ycium previously noted this occuring in
ferocissimum (Box Thorn). This this species and feel it has the
increase reflects both the potential to be an environmental
increased usage of these areas, by weed in coastal areas of Australia,
recreational boaters and searching especially since it occurs naturally
of rocky headlands by the author. in coastal areas from south of
Several of these weeds were Rockingham to Esperance. It also
recorded from the new beach has seed spread by birds and it
being developed at Broun Bay at could potentially spread
the base of the causeway. throughout the island.
Sea Spurge is currently spreading Examples of plants in the base
along the north-western beaches area which are known bushland
of Garden Island, and will weeds in the Perth Area are*.
become a major component of Brassica tournefortii (Prickly
the strand flora. This population Turnip), Conyza albida (Tall
probably arrived on a boat or in Fleabane), Pseudognaphalium luteo-
gear which had seeds present on album (Jersey Cudweed), Senecio
it. The size of the population vulgaris (Common Fireweed),
suggests that this species has been Minuartia mediterranea (Sand
resident for some time (Keighery Wort). The following species are
and Dodd, 1997). unlikely to invade bushland on
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Table 1. Unburnt Callitris/Melaleuca/ Acacia sites.
Key
Gl,3, 4 Woodland quadrats on Garden Island, Swan Coastal Plain Survey (SCP).
GB Burnt Melaleuca quadrat on Garden Island
WP Unburnt quadrat at Woodmans Point,SCP Survey
TD Unburnt Callitris quadrat at Trigg Dunes, SCP Survey
G1 G3 G4 GB WP TD
Callitris preissii * * * *
Acacia rostellifera * * *
Acanthocarpus preissii * * * * *
Acrotriche cordata *
Agrostis preissii *
*Aira cupiana * * * *
*Anagallis arvensis * *
Apium anuum * *
*Briza maxima *
Calandrinia calyptrata * *
*Catapodium rigidum * *
*Cerastium glomeratum * *
Clematis microphylla * * * * *
Comesperma integerrimum * *
Conostylis candicans *
Crassula colorata *
*Crassula glomerata * * *
Eremophila glabra
*Erhrata longiflora
Eucalyptus gomphocephala
*Euphorbia peplus
* * * * * *
*Galium murale
* *
Hardenbergia comptoniana
* *
*Lagurusovatus
*
Lasiopetalum oppositifolium
*
Lepidium puberulum
* *
Leucopogon australis
*
Melaleuca acerosa
* * * *
Melaleuca lanceolata
*
Myosotis australis
* *
*Myrsiphyllum asparagoides
*
Oxalis perrenenans
* * *
Parietaria debilis
* * *
Phyllanthus calycinus
*
Poa poiformis
* *
Poranthera microphylla
* * * *
Rhagodia baccata
*
Santalum acuminatum
* * * * *
Spyridium globulosum
Senecio lautus
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Table 1 (cont.)
G1 G3 G4 GB WP TD
* * *
*Sonchus oleraceus
* *
*Solanum nigrum
* *
Solanum symonii
* *
Stipa flavescens
*
Thomasia cognata
*
Thysanotus patersonii
* * * *
*Trachyandra divaricata
* * *
Trachymene caerulea
* * * *
Trachymene pilosa
*
*Vulpia myorus
* *
*Zantdescia aethiopica
Total 25 21 16 20 18 16
No. Weeds 9 3 7 5 6 6
% Weeds 36 14 44 25 33 37
Garden Island: Conium maculatum help estimate the potential of
(Hemlock), Cotula bipinnata (Fern weed species in these com¬
Cotula) and Digitaria sanguinalis munities a series of monitoring
(Crab Grass) and will probably quadrats were established on the
remain in the base area. island and in similar com¬
munities at Woodmans Point on
the mainland.
B) DISTRIBUTION, ABUNDANCE
Species diversity of unburnt
AND THREAT OF WEEDS
woodlands and shrublands (data
RECORDED
from Gibson et ai, 1994) ranges
1) Weeds on Garden Island and from 16 -25 species per 100m2
communities on the adjacent (Table 1). The percentage of weeds
mainland. in these sites ranges between 14
There is little information and 37%. These weeds are nearly
available on the distribution, all small annuals, except for the
abundance or threat potential tuberous herb T rachyandra
(ability of the species to both divaricata. Normally in such areas
invade and multiply in native there are moss covered or bare
plant communities) of most of areas free of shrubs or herbs. These
the weeds recorded for Garden micro-sites are the location of
Island. Most weed lists simply many of the unusual herbs found
record the presence of a species, on Garden Island (eg: Myostis
rather than detailing their spread, australis, Cynoglossum australe and
abundance or threat potential. Lepidium puberulum) and not on
Except for a few major weeds this the adjacent mainland. These bare
is the case for Garden Island. To areas also lower fuel loads in these
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Table 2. Weeds and Fire - Woodman’s Point, 1992.
Key
a, b, c, d,e 100m2 quadrats
a Foredune in recreation area
b Swale in recreation area
c,d,e Woodman's Point Conservation Area
R Regeneration mode after fire: S=from seed; R= from rootstocks, bulbs or
rhizomes.
GI Weed recorded from Garden Island.
D Dead
a b c d e R GI
Callitris preissii * * * * * S
Acacia cyclops * * * * R
Acacia cochlearis * * * S
Solanum symonii * * S
Melaleuca acerosa * * * R
Melaleuca huegelii * S
* *
*Leptospermum laevigatum S
* * *
*Nicotiana glauca * * * * S
Spyridium globulosum * * S
Hardenbergia comptoniana R
* *
Scaevola crassifolia * * * R
Anthocercis littorea * * * * * s
Olearia axillaris * s
Leucopogon parviflorus * R
Acanthocarpus preissii * R
Clematis microphylla * R
Hardenbergia comptoniana * * * R
Rhagodia baccata * * * R
Comesperma integerrimum * * R
Schoenus grandiflora * * s
*Trachyandra divaricata * * * * * R *
Threlkeldia diffusa * R
*Myrsiphyllum asparagoides * D D D R *
*Pelargonium capitatum * *
R/S
*Anagallis arvensis * * s *
*Avena barbata * s *
Carpobrotus virescens * * * s
*
*Carpobrotus edulis s
*
*Arenaria serpyllifolia s
*Brassica tournefortii * s *
*Conyza albida * s *
*Dishisma arenaria * s *
*Erhrata longiflora * * * * s *
*Galium murale * QJ *
*Galium aparine * s
*Lactuca serriola * oc
*Bromus diandrus * * S *
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Table 2 (cont.)
a b c d e R Gl
* * * * *
*Lagurus ovatus S
*Lolium rigidum * S *
*Sonchus oleraceus * * * S *
*Solanum nigrum * S *
*Euphorbia terracina * S
Crassula colorata * * S
*Crassula glomerata * * * * S *
*Dittrichia graveolens * * S *
*Phytolacca octandra * S *
*?Corrigola littoralis * * S
Totals 23 20 21 21 19
No. Weeds 10 11 11 11 8
% Weeds 43 55 52 52 42
fire intolerant com-munities. could permanently alter these
They are unfortunately the areas communities. Many shrubs and
first colonised by weeds, trees will be planted as ammenity
especially after fire. species in the developed areas of
Garden Island and require
As a comparison, at Woodmans
considerable care in selection as is
Point most of the Callitris Forest
currently practised by the Navy.
was burnt in summer 1990. A
series of quadrats were established 2) Weeds on Garden Island
in this area in early 1992 (Table 2).
In Appendix 1 all recorded weeds
Here the species diversity ranged
of Garden Island are listed with
from 19-23 species per 100m2.
notes on the major area of
However, the percentage of weeds
occurrence on the island and the
ranged from 42-55%! Of
species threat potential (this is
particular concern was the
based on information in Dixon
appearance of two perennial
and Keighery, 1995). In summary-.
shrub weeds, L eptospermum
- the most serious weed of
laevigatum (Victorian Tea Tree)
Garden Island is Arum lily
axi Nicotiana glauca (Tree
Tobaco) as weeds in these sites. - another potentially serious
Grassy weeds invaded the open weed is Bridal Creeper
moss areas which were killed by
- there are
the fire.
30 widespread weeds
Currently we can observe that on
(Homeria and Trachyandra
the mainland weed invasion
could be serious)
occurs markedly after fire in these
9 beach weeds
communities. Some of these
weeds are long lived shrubs that 6 weeds of rocky headlands
67
(including L ycium and The potential for a weed to
L avatera) become serious can be illustrated
10 Settlement weeds by Agonis flexuosa (Peppermint). It
is recommended that the Agonis
27 weeds with no data
flexuosa plants be removed as soon
11 “Extinct” weeds
as practicable, as these are seeding,
6 weeds just persisting and already are major weeds in
4 very localized weeds Kings Park and Yanchep. They
(Agonis needs to be removed) will spread rapidly after fire into
the woodlands. Continual
(a) serious or potentially serious
vigilance is required to prevent
weeds-This information shows
the development of more serious
that there are five serious or
weeds.
potentially serious weeds present
on the Island that require Both Homeria (Cape Tulip) and
management attention. These are Trachyandra are unpalatable and
Zantdeschia aethiopica (Arum Lily), could spread after disturbance,
Asparagus asparagoides (Bridal such as fire. Bridal Creeper is
Creeper), Trachyandra divaricata controlled by Tammar grazing.
(Strap Lily) and Homeria flaccida This could also explain the low
(Cape Tulip). numbers of the other listed
annual weeds. Lycium (Boxthorn)
Other potentially serious weeds
and Lavatera (Tree Mallow) are
of coastal woodlands in the Perth
serious weeds of rocky islets near
area and present on Garden Island
Perth, and probably would only
are, Brassica tournefortii (Prickly
be of concern on headlands on
Turnip), Euphorbia peplus (Petty
Garden Island. The potato creeper
Spurge), Urtica urens (Stinging
Nettle) and the grasses A vena (Anredera cordifolia) is a serious
weed in Eastern Australian
barbata (Wild Oats), Bromus
rainforest and along disturbed
diandrus (Great Brome) and
creeklines and swamps around
Ehrharta longiflora (Annual Veld
Perth. It could be considered a
Grass). These seem to be present at
low threat, but given that Arum
low levels on the island, but
Lily has similar preferences, it
require monitoring. The above
should be removed.
weeds have replaced the native
Parietraria debilis as an winter
understory (and the moss swards
CONCLUSION
and rarer spring annuals) in many
island and coastal sites in Western Garden Island was the site for the
Australia. Perhaps Tammar first settlement on the west coast
grazing is holding these weeds in of Western Australia in 1829.
check on Garden Island and the Since that time there have been
Navy’s careful management of continual introductions of alien
these native grazers is worthy of plants onto the island. Garden
considerable praise as they are Island, however, unlike Rottnest
probably the key to successful was not extensively cleared or
management of palatable weeds altered by changing fire regimes
on the island. and today contains a series of fire
68
intolerant plant communities. and Harris, J. Greening Western
These are the Melaleuca and Australia, Perth, pp. 43-144.
Callitris woodlands, and the
ELLIOT, W.R. and JONES, D.L.
Acacia shrublands. These simple
1990 Encyclopedia of Australian
communities are also very prone
Plants Suitable for Cultivation.
to weed invasion, especially
Volume 5. Lothian Publishing,
species not palatable to Tammars.
Melbourne.
The current efforts to control
such weeds are commended as is GARDEN ISLAND ENVIRON¬
the quarantine of new weeds MENTAL ADVISORY COM¬
being introduced around the MITTEE, 1996. Garden Island
base. Efforts need to be directed
Environmental Advisory Com¬
to removing other invasive un¬
mittee Report of Activities 1995—
palatable weeds, such as Homeria
1996. Department of Defence,
flaccida present on the island.
Canberra.
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70