The Naturalized Vascular Plants of Western Australia 1
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12 Plant Protection Quarterly Vol.19(1) 2004 Distribution in IBRA Regions Western Australia is divided into 26 The naturalized vascular plants of Western Australia natural regions (Figure 1) that are used for 1: Checklist, environmental weeds and distribution in bioregional planning. Weeds are unevenly distributed in these regions, generally IBRA regions those with the greatest amount of land disturbance and population have the high- Greg Keighery and Vanda Longman, Department of Conservation and Land est number of weeds (Table 4). For exam- Management, WA Wildlife Research Centre, PO Box 51, Wanneroo, Western ple in the tropical Kimberley, VB, which Australia 6946, Australia. contains the Ord irrigation area, the major cropping area, has the greatest number of weeds. However, the ‘weediest regions’ are the Swan Coastal Plain (801) and the Abstract naturalized, but are no longer considered adjacent Jarrah Forest (705) which contain There are 1233 naturalized vascular plant naturalized and those taxa recorded as the capital Perth, several other large towns taxa recorded for Western Australia, com- garden escapes. and most of the intensive horticulture of posed of 12 Ferns, 15 Gymnosperms, 345 A second paper will rank the impor- the State. Monocotyledons and 861 Dicotyledons. tance of environmental weeds in each Most of the desert has low numbers of Of these, 677 taxa (55%) are environmen- IBRA region. weeds, ranging from five recorded for the tal weeds, recorded from natural bush- Gibson Desert to 135 for the Carnarvon land areas. Another 94 taxa are listed as Results (containing the horticultural centre of semi-naturalized garden escapes. Most Total naturalized flora Carnarvon). However, these figures for are herbaceous annuals or grasses with The total number of plants listed, as repro- the remote desert regions are probably, the largest groups being the Poaceae ducing unaided by man (naturalized) in in part, an artifact of recording effort. The (196), Asteraceae (115), Papilionaceae Western Australia is 1233 (Tables 1, 4 and Tanami Desert in the Northern Territory (106) and Iridaceae (53). 5). This total is composed of 12 ferns, 15 has 39 weeds recorded (Albrecht 1999) The largest numbers of weeds are gymnosperms, 345 monocotyledons and compared to the portion in Western Aus- recorded from the natural regions en- 861 dicotyledons (Table 5). Forty seven tralia with seven. compassing the capital Perth, with 801 taxa are listed as currently not naturalized and 705 recorded for the Swan Coastal (Table 2). Keighery (1995) listed a total of Most widespread weeds Plain and Jarrah Forest Bioregions re- 1033, composed of six ferns, seven gym- There are 60 weeds, which have been re- spectively. nosperms, 318 monocotyledons and 701 corded in 10 or more IBRA regions. The Most weeds are still localized in ex- dicotyledons. With increasing scrutiny most widespread weed is Sonchus oler- tent with only 60 occurring in 10 or more and population increase the number of aceus (20 regions), followed by Cenchrus natural regions, the vast majority in less naturalized plants continues to increase. ciliaris and Solanum nigrum (17), Pseudog- than three, suggesting that further spread Currently the largest groups are the naphalium luteo-album and Citrullus lanatus will occur in most weeds. families Poaceae (Grasses) with 196 taxa, (16), Sisymbrium orientale (15) and Emex followed by the Asteraceae (Daisies) with australis and Tribulus terrestis (14). Introduction 115, the Papilionaceae (Peas) with 106 and While climate does restrict weeds in In 1994 the senior author prepared a check- the Iridaceae (Iris family) with 53. These a similar fashion to all plant species, the list of the naturalized weeds of Western families comprise 38% of the total number median regional occurrence of weeds is Australia (WA), with particular reference of naturalized taxa recorded in the State. currently between two and three regions. to environmental weeds (Keighery 1995). By climate alone it could be between five Since then, a weed field guide (Hussey et Environmental weeds and eight. We can expect that increases in al. 1997) has been produced and a consid- Of the total 1233 naturalized taxa, 677 ranges of most naturalized taxa. erable amount of further survey work has taxa (55%) are listed as occurring and been undertaken. As a consequence, the reproducing (naturalized) in reasonably Origin of Western Australia’s weeds checklist needed updating. intact bushland in Western Australia (en- Although the vast majority of weeds are The preparation of a State Environ- vironmental weeds). These are composed exotics there remains a small but growing mental Weed Strategy (Ecoscape and of seven Ferns, three Gymnosperms, 197 portion of the weed flora that is native Department of Conservation and Land Monocotyledons and 470 Dicotyledons. to Australia. There are three ferns, five Management 1999) initiated this update, The percentage of these weeds has not gymnosperms, one monocotyledon and as the Strategy required: declined since the previous checklist. 28 dicotyledons (37) that are native to • the update of the 1995 list; Eastern Australia. These are nearly all en- • all weeds to be geographically located Garden escapes vironmental weeds (Keighery 2002), some in an Australia wide system, Interim Ninety four taxa are recorded as garden of potential or actual major significance. Biogeographic Regions of Australia escapes or outcasts. Garden escapes Forty-nine taxa are Western Austral- (IBRA regions, Thackway and Creswell (‘plants growing spontaneously outside ian natives, comprising; four ferns, one 1995); and a fenced area, or as a weed in a sown or Gymnosperm, six Monocotyledons and • the ranking of the listed environmental planted community’ or ‘plants that are 38 Dicotyledons. Many are native to weeds. reproducing and expanding within the northern Western Australia (Table 1) but This paper utilizes these data to prepare habitat and have maintained themselves are introduced to southern Western Aus- a new checklist of weeds of Western over time, without human assistance’, tralia. These taxa are frequently not segre- Australia, with their distribution in IBRA Keighery 1983) are recorded in Table 3. gated in flora or weed checklists and yet regions. These taxa may be in the process of be- several are serious environmental weeds Many Australia wide checklists of coming naturalized. These are part of a (Keighery 2002). weeds list only exotics, but this paper lists long-term project documenting potential Australian natives feature prominently all regardless of origin. The paper also weeds from plantings and gardens, for in the list of Garden Escapes (Table 3), lists taxa that at one time were considered example Keighery (1986). where there are 17 Western Australian Plant Protection Quarterly Vol.19(1) 2004 13 natives and five Eastern Australian na- is equivocal and they are not listed until Publishing Service, Canberra). tives. This suggests that these groups may further information is obtained. Hill, K.D. (1998). Cupressaceae. In ‘Flora provide a major new reservoir of future of Australia. Volume 48. Ferns, Gymos- environmental weeds. Acknowledgements perms and Allied Groups’, ed. A.E. Information on weed taxonomy, occur- Orchard. pp. 569-88. (ABRS/CSIRO Native or naturalized rences and impacts were provided by Australia). There are still continuing issues with de- Kate Brown, Bob Dixon, Jon Dodd, John Hussey, B.M.J., Keighery, G.J., Cousens, termining the native or naturalized status Hoskings, Brendan Lepschi, Sandy Lloyd, R.D., Dodd, J. and Lloyd, S.G. (1997). of widespread tropical naturally weedy Chris Robinson, Rod Randall, John Stretch ‘Western Weeds’. (Plant Protection So- taxa and cosmopolitan wetland taxa of and Neville Walsh. Historical records were ciety, Perth). temperate areas. (Keighery 2002). Some consulted at Melbourne Herbarium. None Jacobs, S.W.L. and Hastings, S.M. (1993). new examples listed here include the of this would have been possible without Bromus. In ‘Flora New South Wales. status of Physalis minima, Cardiospermum constant use of the collections of the West- Volume 4’, ed. G. Harden, pp. 628-33. halicacabum and Oldenlandia corymbosa. ern Australian Herbarium and the result- (University of New South Wales Press, There are also a series of native taxa ant taxonomic work on these. Sydney). within their normal ranges (Pteridium Keighery, G.J. (1983). Garden escapes esculentum, Ptilotus polystachyus, Acacia References (When is a weed not a weed) in West- saligna, Chenopodium pumilio, Podotheca Albrecht, D. (1999). ‘Weeds of the Tanami’. ern Australia. Australian Garden Journal gnaphaliodes, Muehlenbeckia adpressa and (Normandy NFM Ltd., Asprint Print, 2, 148-51. Vittadinia australasica) that act as weeds Alice Springs). Keighery, G.J. (1986). Garden escapes on in grazing systems in southern Western Appleby, M. (1997). Sir Frederick Samson Rottnest Island: An annotated Check- Australia. Most of these are listed in this Park flora list. Unpublished Report for list. Landnote 3/86. (CALM). paper. the City of Fremantle. Keighery, G.J. (1991). Weeds of John For- Another group of native species are in- Armstrong, P. (1993). Vegetation and flora rest National Park along Jane Brook. creasers in grazing systems where they are survey of the Shire of Kalamunda Vest- CALM Internal Report. relatively unpalatable; they are frequently ed Reserves, Volumes I and II. (Shire of Keighery, G.J. (1995). An annotated list of listed as weeds in agricultural texts, but Kalamunda). the naturalised vascular plants of West- are not considered as weeds by most bota- Bennett, E.M. (1995). Plant species of the ern Australia. In ‘Invasive weeds and nists and are not listed in this paper. Kings Park Bushland. Western Austral- regenerating ecosystems in Western A small group of native species are ian Naturalist 20, 97-118. Australia’, ed. G.R. Burke. (Institute weeds of tropical farming systems, such Briggs, B.G., Wiecek, B. and Whalen, A.J. of Science and Technology, Murdoch as Echinochloa elliptica in rice crops, these (1992). Veronica. In ‘Flora of New South University, Murdoch). species when recorded are listed in this Wales.