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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 61 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 63 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 64 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 65 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 * 66 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. GARDEN ISLAND ENVIRON¬ REFERENCES MENTAL ADVISORY COM¬ MITTEE, 1997. Garden Island BAIRD, A.M. 1958. Notes on the Environmental Advisory Com¬ Regeneration of Vegetation of mittee Report of Activities 1996- Garden Island after the 1956 Fire. 1997. Department of Defence, Journal of the Royal Society of Canberra. Western Australia 41:102—107. 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