124 Plant Protection Quarterly Vol.16(3) 2001 Of these, A. longifolia var. sophorae, K. ambigua, L. laevigatum, P. undulatum and Australian plants as weeds in Victoria S. heterophylla are the worst weed species in the State, far more serious where they G.W. Carr, Ecology Australia Pty. Ltd., 88B Station Street, Fairfield, Victoria occur than most exotic non-Australian species, including all Weeds of National 3078, Australia. Significance except Asparagus asparagoides. Acacia longifolia var. sophorae will destroy almost all indigenous vegetation and its Abstract naturalized well outside their pre-Euro- dependent fauna in coastal and near- Australian plants are very well known as pean range. All form dense monospecific coastal western Victoria on sandy sub- environmental weeds overseas where stands which eliminate all or most indig- strates (i.e. most indigenous vegetation re- they constitute some of the most devastat- enous plant species and the dependant maining). The Grampians for example, a ing of all biological invasions. The most fauna. The anthropogenic facilitation of biome of international significance, is un- recent Census of the Victorian flora (pro- these upsurges of indigenous taxa are dis- der extreme threat from invading Acacia duced by the State Herbarium) lists 3480 cussed; they include altered fire regimes, longifolia var. longifolia and A. longifolia var. indigenous taxa (species, subspecies vari- total grazing pressure involving feral and sophorae but so far little if any management eties, forms) and 1142 naturalized, extra- indigenous vertebrates, seed dispersal by action has been taken to address these in- Australian taxa, as well as a few natural- exotic vertebrates (mostly birds) and by vaders. ized from other Australian States. Some 16 humans and motor vehicles. The particular problem posed by in- species are listed in a recently recognized Of the approximately 200 naturalized vading Australian plants relates to per- census category: taxa indigenous and Australian taxa listed (in an appendix), al- ceptions of weediness. Many people are naturalized in Victoria; 17 species are most all are trees and shrubs, with a few reluctant to believe that the invasions are listed as naturalized from other states. Re- vines and perennial herbs. Almost all of management concern; how can a ‘na- cent research has shown that the number have ‘escaped’ from cultivation–gardens, tive’ plant be a weed? For example, it took of taxa naturalized in Victoria from other roadside plantings and farm and forestry approximately 20 years for botanists to states, and taxa indigenous and natural- plantations. Most are of minor concern as convince the Department of Natural Re- ized is far larger. Approximately 200 taxa environmental weeds, occurring as natu- sources and Environment at Portland in of Australian plants have now been re- ralized populations of varying sizes far south-west Victoria that A. longifolia corded as naturalized and the list contin- (sometimes large) in often highly dis- var. sophorae was destroying all heaths ues to grow steadily. Of the 200 odd taxa, turbed situations relatively remote from and heathy woodlands, and that the Aca- approximately 64 occur naturally in Vic- indigenous vegetation which they may cia’s behaviour was not part of some natu- toria, though now naturalized outside otherwise invade. Numerous Eucalyptus ral ‘cyclic’ ecological process. their pre-European geographic range. species, particularly from Western Aus- There are also opposed views in the Two other categories of invasive plants tralia, for example are naturalized on community, sometimes relating to the un- are recognized: hybridization between an roadsides in agricultural landscapes. resolved issue of the definition of natural in situ indigenous species and an exotic A subset of this naturalized flora is of distribution. Many people overlook the species (invasion of genes), and ecologi- extreme concern as environmental weeds catastrophic weediness of Pittosporum cally ‘out-of-balance’ species. and the 20 taxa of most concern are listed undulatum in South Gippsland and the Some 16 hybrid combinations are in Table 1 (with the most seriously inva- Strzelecki Ranges (where it is allegedly known between species of Acacia, Correa, sive in bold). indigenous); it will eliminate almost all Epilobium, Grevillea, Leptospermum, Nico- tiana and Pittosporum. In three cases the ex- Table 1. Australian naturalized plant taxa in Victoria that are very serious otic congeneric is non-Australian. Such environmental weeds. The most invasive are shown in bold. hybrids are mostly rare and of little conse- Taxon Family Life form Natural quence. In some cases however large hy- distribution brid swarms have arisen and intro- gression threatens the genetic integrity of Acacia baileyana Mimosaceae Tree NSW the in situ parent, creating a serious prob- Acacia decurrens Mimosaceae Tree NSW, Qld lem for the conservation of the population Acacia elata Mimosaceae Tree NSW or metapopulation. This is particularly se- Acacia floribunda Mimosaceae Tree/shrub Vic, NSW, Qld rious in the highly promiscuous genus Acacia longifolia var. longifolia Mimosaceae Shrub Vic, NSW, Qld Grevillea, in Acacia mucronata × A. longifolia Acacia longifolia var. sophorae Mimosaceae Shrub Vic, NSW, SA var. longifolia (the latter is exotic) and in Acacia prominens Mimosaceae Tree NSW Pittosporum bicolor × P. undulatum (exotic). Acacia retinodes var. retinodes Mimosaceae Tree/shrub Vic, SA, Tas Ecologically ‘out-of-balance’ species Hakea laurina Proteaceae Shrub WA are indigenous trees or shrubs which be- have as environmental weeds, assuming Hakea salicifolia Proteaceae Shrub NSW structural dominance in vegetation com- Hakea drupacea Proteaceae Shrub WA munities in which they formerly occurred Kunzea ambigua Myrtaceae Shrub Vic, NSW, Tas as a relatively minor component, or they Kunzea ericoides Myrtaceae Shrub Vic, NSW Qld have expanded their range into adjoining Leptospermum laevigatum Myrtaceae Shrub/tree Vic, NSW, Tas vegetation types where, as invaders, they Melaleuca armillaris ssp. armillaris Myrtaceae Tree/shrub Vic, Tas have disastrous impacts on the indig- Melaleuca hypericifolia Myrtaceae Shrub NSW enous biota. The most important (cata- Melaleuca nesophila Myrtaceae Shrub WA strophically invasive) species in this con- Paraserianthes lophantha Mimosaceae Shrub WA text are Acacia longifolia var. sophorae, Pittosporum undulatum Pittosporaceae Tree Vic, NSW, Qld Kunzea ambigua, Leptospermum laevigatum Sollya heterophylla Pittosporaceae Vine WA and Pittosporum undulatum which are also Plant Protection Quarterly Vol.16(3) 2001 125 indigenous (non-wetland) vegetation in the region at various time scales. The biology, ecology and management NGIA initiatives in environmental weed management of invading Australian environmental weed species are discussed and the 200 Jolyon Burnett, Nursery and Garden Industry Australia, PO Box 907, Epping, taxa are listed. Major reasons for their suc- New South Wales 1710, Australia. cess as invaders in often high-quality in- digenous vegetation are a suite of pre- adaptive biological attributes such as serotiny, long-term soil-stored seed banks, Introduction State and local level as well as catchment ability to thrive in low-nutrient substrates, The Nursery and Garden Industry Aus- management trusts and other non- generalist pollination syndromes (often tralia (NGIA) has a long record of interest government organizations. involving birds) and generalist seed- and pro-active involvement in minimiz- Part of the problem can certainly be ad- dispersal syndromes. These attributes also ing the spread and impact of environmen- dressed at the supply end of the issue. make such species pre-eminent invaders tal weeds. This paper will explain the Sound weed risk assessments should be of South African environments where NGIA position, detail some of the initia- done on all new plants entering the coun- many of the same species are destroying tives NGIA has undertaken and make a try. Those invasive plants that are posing vegetation, fauna and catchment values. plea for a commercially realistic and mar- a real risk to remnant bushland and other ket driven approach to the issue of inva- valuable ecosystems and are still in the Note sive plants in gardens. trade need to be identified and removed. The full version of this paper will be pub- Encouraging sensible phase out periods lished in a future edition of Plant Protec- Who to work with and what on along with identifying and promoting al- tion Quarterly. There are almost as many weed related ternatives will ensure cooperation from groups, both government and others, as industry. there are weeds. There is a national strat- Disposal of garden waste and trading egy, each State government has a strategy of plant material between gardeners also and many catchment management trusts plays a significant part. These pathways and local government councils also have can only be addressed by public educa- weed management strategies. Many of tion. The public do not see their favourite these strategies also include lists of plants plants as weeds. Moves to include Aus- deemed by the authors to be environmen- tralian plants in weeds lists, without ex- tal weeds. plaining to the public the basis for such Very few of these lists, if any, are sup- classification, simply brings the whole ported by any form of weed risk assess- idea of environmental weeds into disre- ment. Most reflect the philosophical bent pute. of the organization or author.