Plant Protection Quarterly Vol.16(3) 2001 133 Australian plants can also become weeds of crops, lawns and waste places. A challenge for our values: Australian plants as weeds The CSIRO Handbook of Australian Weeds (Lazarides et al. 1997) lists large numbers of native plants recorded as crop Tim Low, 6 Henry Street, Chapel Hill, Queensland 4069, Australia. and pasture weeds. Success as weeds of Australian species of Rumex L. and Commelina L. matches the success of exotic species within the same genera. In the Summary Riverina of New South Wales, nine of the Australian plants can become weedy In only a few instances have acciden- ten most commonly recorded weeds of when they travel outside their original tally translocated plants become serious rice are locally native plants (McIntyre range as seeds transported accidentally weeds. Examples include bulrush (Typha and Barrett 1985). or as cultivated plants. Few accidentally orientalis C.Presl) from eastern Australia, Australia even has plants that are now translocated plants become serious now invading wetlands near Perth, and threatened species in the wild, but which weeds but many cultivated plants have, Juncus usitatus L.Johnson and J. poly- grow mainly in degraded situations as especially garden plants. Many species anthemus Bucken (and their hybrids) from roadside weeds. The nationally endan- also become highly invasive within their eastern Australia found invading pastures gered Lepidium hyssopifolium Desv. is one original range. south of Perth (Hussey et al. 1997); also such. In Tasmania it occurs at 28 sites, only Garden writers have been advocating Marsilea mutica Mett. in Tasmania (Roze- one of which could be described as natu- Australian plants since the 1830s. Very felds et al. 1999). More species are likely to ral. Kirkpatrick and Gilfedder (1998) note: few native plants were popular in gar- become problematic in future, for example ‘The majority of sites are on roadsides un- dens until recently, but those that were black spear grass (Heteropogon contortus derneath exotic tree species, with a sub- include several of today’s worst weeds. (L.) P.Beauv. ex Roem. & Schult.) in cen- stantial minority in the home yards of These plants had a long head start over tral Australia (Peter Latz personal com- farms’. When cultivated in Melbourne for species entering cultivation more re- munication) The number of accidentally conservation it escaped onto a nearby cently. We can thus expect many more translocated species is probably underes- footpath and is now spreading there as a serious weeds in future, for example pos- timated due to uncertainty about pre-Eu- weed (Neville Scarlett personal communi- sibly Pittosporum ferrugineum. Victoria ropean distributions. For example mimosa cation). Several threatened Acacia species, has the most weedy Australian garden bush (Acacia farnesiana (L.) Willd.), often for example A. perangusta (C.T.White) plants. Several species have established considered exotic despite Leichhardt’s Pedley also do well on disturbed road south of their original range, and others eighteenth century record from remote verges. have spread from eastern to western north Queensland (Leichhardt 1847), has Plants multiplying within their original Australia, and vice versa. probably expanded its range with stock range cause many conservation problems In Australia today an ‘exotic’ plant to movements. It is a very serious weed. (Low in press). The threats posed by sweet most people is one from overseas, and a Plants may also establish feral popu- pittosporum (Pittosporum undulatum ‘native’ plant a plant from Australia. But lations when they are cultivated outside Vent.), burgan (Kunzea ericoides (A.Rich.) ‘exotic’ should apply to any plant estab- their original range as garden, timber, J.Thompson) and coast tea tree (Lepto- lished outside its normal distribution. aquarium, land rehabilitation, arboretum spermum laevigatum (Gaertner) F.Muell.) Gardens of Australian plants should not or tannin plants. Deliberately translocated are well documented (Mullett 2001, Carr be called ‘native gardens’ but ‘national plants are causing more problems than 2001). In other examples, broad-leaved tea gardens’. Whether gardeners grow Aus- accidentally translocated plants because tree (Melaleuca viridiflora Solander ex tralian or foreign plants matters less than many more species and individuals are Gaertner) invasion of grasslands on Cape whether they grow invasive or benign translocated. Garden plants provide the York Peninsula poses a threat to the en- plants. largest pool of invasive species. They are dangered golden-shouldered parrot considered further below. (Psephotus chrysopterigius Gould) (Garnett Overview of the problem Plants become weeds within their origi- and Crowley 1997, 2000), and rainforest Australian plants as weeds have not re- nal range when they multiply in numbers invasion of buttongrass (Gymnoschoenus ceived adequate attention, even though and displace other life forms. This can be a sphaerocephalus (R.Br.) Hook.f.) moors in they cause the same range of problems as response to changing fire regimes, Tasmania is potentially a threat to the en- foreign weeds, albeit on a smaller scale. changed grazing pressure, nutrient en- dangered orange-bellied parrot (Neophema Australian plants invade gardens, farms, richment, soil disturbance, or a combina- chrysogaster Latham.) (Low in press). natural habitats, and pose threats to rare tion of these. Woody weed invasion of These invasions, and also the ecological fauna. pastures in western New South Wales and problems caused by rainforest expansion Australian plants can become weedy Queensland is the best known example. into wet sclerophyll forest in the Wet either within or outside their original Kleinschmidt and Johnson (1977) list 43 Tropics (Harrington and Sandserson range. Plants are taken outside their origi- native woody weeds in Queensland in- 1994), pose conceptual problems, because nal range either accidentally or deliber- cluding Eucalyptus L’Hér. Acacia Miller, they probably represent vegetation re- ately. They travel accidentally on vehicles Melaleuca L. and Eremophila R.Br. species. sponding naturally to a cessation of Abo- as seeds carried in soil (Wace 1977), hay, In Tasmania the rare endemic shrub riginal burning (Low in press). A similar dung or attached to animals or clothes. Melaleuca pustulata Hook.f. has become a quandary is posed by coast tea tree. If it Seeds often travel from inland pastures to very serious woody weed on two sheep was confined to coastal dunes only by past coastal ports with movements of stock farms (Low in press). The displacement of Aboriginal fires (i.e. by human interven- (Macdonald 1887, Gray and Michael 1986, Kangaroo grass (Themeda triandra Forrsk.) tion), should we not allow it to reclaim its Kloot 1985). In other examples, plants na- pastures by black spear grass in Queens- former habitat further inland? tive to mainland eastern Australia have land is also well documented (Shaw 1957). It is important to note that Australian established new populations in Tasmania Spear grass seed awns are so troublesome animals as well as plants become ecologi- (Rozefelds et al. 1999) and Western Aus- to sheep that farmers were forced to con- cal and economic pests. Many species now tralia (Hussey et al. 1997). vert to cattle. live outside their original ranges as a 134 Plant Protection Quarterly Vol.16(3) 2001 result of accidental and deliberate trans- director of the Melbourne Botanic Gar- are significant weeds around Brisbane locations (Low in press). Examples that dens after von Mueller. In this, the first (Low 1993), and Darwin has only three are serious pests include redback spiders book devoted to growing native plants, naturalised species (Acacia dunnii (Latrodectus hasseltii ) in eastern Australia Guilfoyle listed hundreds and hundreds (Maiden) Turrill, A. mangium Willd., A. (Low in press), pandanus leafhoppers of species, including 53 hakeas and 127 mountfordiae), none of which is serious (Jamella australiae Kirkaldy) in southern wattles, in what was less a gardening (Colin Wilson personal communication) Queensland (Smith and Smith 2000), crim- book than a dictionary of useful plants. The problems appear to be worst in Vic- son rosellas (Platycercus elegans Gmelin) Around the same time, horticulturist toria (and around Adelaide and Canberra) on Norfolk Island (Garnett and Crowley Edward Pescott spoke at horticultural so- because of a large human population 2000), and masked owls (Tyto novae- cieties around Victoria promoting ‘Aus- growing native plants, and a highly dis- hollandiae Stephens) on Lord Howe Island tralian flowers for Australian gardens’ turbed environment offering many oppor- (Garnett and Crowley 2000). Other animal (Pescott 1912). Pescott, like James, could tunities for establishment of weeds, both species have become pests in situ, by in- complain that native plants had been ne- native and introduced. creasing their population density, for ex- glected. ‘Australian patriotism gives its ample kangaroos, koalas and mosquitoes. patronage very largely to industrial, po- Directions of spread Australian plants, animals and diseases litical, and similar subjects;’ he observed, Large numbers of species have natural- have also become very serious pests over- ‘but in horticulture it has apparently been ised well south of their original ranges. seas (Low 1999). the fashion that any plant which could Umbrella tree (Schefflera actinophylla) was carry the distinction of being imported is originally found about as far south as Garden plants far preferable to one which owns Aus- Gladstone but is now found south to Syd- History tralia for its native habitat’. ney. Cadagi (Corymbia torreliana), from the The first Australian gardening book ap- It was not until the 1950s that Austral- Atherton Tableland is very invasive peared in 1835 (Crittenden 1985). It was ian plants genuinely became popular. Na- around Brisbane (Low 1993). Silky oak Thomas Shepherd’s Lectures on the Horti- tive gardening books finally appeared, in- (Grevillea robusta A.Cunn. ex R.Br.) and culture of New South Wales, and it con- cluding Australian plants for the garden by lemon-scented tea tree (Leptospermum cerned itself only with vegetables. A sec- wildflower devotee Thistle Harris (Harris petersonii F.M.Bailey) from southern ond book appeared just three years later, 1953). The Society for Growing Australian Queensland and northern New South covering flowers, and it included native Plants formed in Victoria in 1957. Wales are now invasive in Victoria (Carr species. It was the Manual of practical gar- What becomes clear from this history is 1993). Plants from the mainland are suc- dening adapted to the climate of Van Diemen’s that very few native plants were genu- ceeding in Tasmania (Rozefelds et al. Land containing plain and familiar directions inely popular in gardens in the past, but 1999). Southward range extensions have for the management of the kitchen, fruit and those that were include many of today’s also occurred among insects, such as the flower gardens, nursery, greenhouse and forc- worst weeds. Sweet pittosporum seeds pandanus leafhopper (Jamella australiae ing department for every month of the year, by were selling in the United States by 1826 Kirkaldy) and orange palmdart (Cephrenes Daniel Bunce (Crittenden 1985). This book (Mack 1991). James spoke very highly of augiades Felder), and presumably repre- was revised and republished in Mel- sweet pittosporum as a hedge plant in sent a response to natural global warming. bourne as The Australian Manual of Horti- 1892. The forty plant species mentioned Plants are also spreading between tem- culture (Bunce 1850). Bunce encouraged by Pescott (1912) included four of today’s perate eastern and Western Australia readers to dig up young forest shrubs for worst invaders: sweet pittosporum, blue- (Hussey et al. 1997), into regions with transfer to the garden. Many of the species bell creeper (Sollya heterophylla Lindley) , matching climates. South-western Aus- he recommended (Dillwynia Smith, Cootamundra wattle (Acacia baileyana) tralia has no native rainforest plants but Daviesia Smith, Prostanthera Labill., Zieria and golden wreath. These plants have a the region around Walpole has an ideal Smith species) prefer low-nutrient soils hundred year’s head start over species climate for temperate rainforest species. and do not grow well in Melbourne today. brought into cultivation more recently. Large numbers of plants from Western Ferdinand von Mueller’s Select plants We are thus likely to see many more Aus- Australia are naturalizing in Victoria readily eligible for Victorian industrial culture tralian plants on our weed lists in future. (Pigott 2001). (1881), spoke highly of some plants such A species such as rusty pittosporum A third direction of spread with severe as flame tree (Brachychiton populneus (Pittosporum ferrugineum W.T.Aiton ex. ecological implications is from mainland (Schott & Endl.) R.Br.), which now sprouts Dryand.), which is unknown to most Australia to Norfolk and Lord Howe Is- as a weed around Sydney and Brisbane. In weed experts today but which is highly lands. Sweet pittosporum is one of Lord the Handbook of Australian horticulture invasive near the Gold Coast (Low in Howe’s two worst weeds (Ian Hutton per- (1892), H.A. James devoted thirty pages to press), appears destined to become a ma- sonal communication) Australian plants. James was the first to jor weed. There may be many similar spe- push native species strongly, observing cies on their way to becoming serious in- Defining ‘Native plants’ that ‘plants and flowers indigenous in vaders. In Australia today, an ‘exotic’ plant, to Australia do not appear to have received most people, is one from overseas, and a from Colonial nurserymen and amateur Regional perspective ‘native’ plant a plant from Australia. But gardeners, that consideration which their Victoria has far more invasive Australian The World Conservation Union (IUCN) beauties may fairly claim’. Many of to- plants than other states. Carr (2001) lists (McNeely 2000), defines an alien (or ex- day’s weeds star in his weighty tome, in- more than 200 species. At Mt. Martha (site otic) species as one that is ‘introduced out- cluding Cootamundra wattle (Acacia of a former arboretum) 38 species have side its normal past or present distribu- baileyana F.Muell.), golden wreath wattle been recorded (Carr et al. 1991). Fewer tion’. By this definition all of the plants (Acacia saligna (Labill.) H.L. Wendl.), than 60 species are recorded from West- mentioned here are ‘exotic’ invaders. Aus- Queensland silver wattle (A. podalyriifolia ern Australia (Greg Keighery, unpub- tralians should not let political boundaries Cunn. ex G.Don), coast teatree and sweet lished data), and far fewer species from dictate biological categories. Australia is pittosporum. Queensland and the Northern Territory. one of world’s largest countries, and had The next milestone was Australian Only three species (Schefflera actinophylla the continent been carved up into smaller plants suitable for gardens, parks, timber re- (Endl.) Harris, Corymbia torelliana nations, as Europe is, a gardener in Syd- serves etc. (1911), by William Guilfoyle, F.Muell., Nephrolepis cordifolia (L.) Presl) ney would not call a plant from Perth a Plant Protection Quarterly Vol.16(3) 2001 135 ‘native plant’. Perth is as far from Sydney sclerophyll forest in the wet tropics of on plant biodiversity. Plant Protection as Portugal from Russia or Belgium from Queensland due to invasion by rainfor- Quarterly 16, 117-21. Arabia. Gardens of Australian plants est. Pacific Conservation Biology 1, Pescott, E.E. (1912). Australian flowers for should not be called ‘native gardens’ but 319-27. Australian gardens. (F.W. Niven, Mel- ‘national gardens’. Harris, T. (1953). ‘Australian plants for the bourne). Gardening with native plants is com- garden’. (Angus and Robertson, Syd- Pigott, P. (2001). Transcontinental inva- monly thought to benefit the environ- ney). sions of vascular plants in Australia, an ment. But as Wolschke-Bulmahn (1996) Hussey, B.M.J., Keighery, G.J., Cousens, example of natives from south-west notes “Advocacy of the use of ‘native’ R.D., Dodd, J. and Lloyd, S.G. (1997). Western Australia weedy in Victoria. plants may be a moral response to some of ‘Western weeds: a guide to the weeds Plant Protection Quarterly 16, 121-3. the many environmental problems we of Western Australia’. (Plant Protection Rozefelds, A.C.F., Cave, L, Morris, D.I. have all over the earth. However, there is Society of Western Australia, Perth). and Buchanana, A.M. (1999). The weed no reason for a native plant doctrine, nor James, H.A. (1892). ‘Handbook of Austral- invasion in Tasmania since 1970. Aus- for the assumption that so-called native ian horticulture.’ (Turner and Hender- tralian Journal of Botany 47, 33-48. plants would serve environmental goals. son, Sydney). Shaw, N.H. (1957). Bunch spear grass The segregation of good and bad plants, Kirkpatrick, J.B. and Gilfedder, L. (1998). dominance in burnt pastures in south- natives and non-natives, and the condem- Conservation of weedy natives: Two eastern Queensland. Australian Journal nation of the latter as aggressive invaders Tasmanian endangered herbs in the of Agricultural Research 8, 325-34. is too simplistic and helps to mask prob- Brassicaceae. Australian Journal of Ecol- Smith, N.J. and Smith, D. (2000). Studies lems rather than engage them.” ogy 23, 466-73. on the Flatid Jamella australiae Kirkaldy Gardeners should grow non-invasive Kleinschmidt, H.E. and Johnson, R.W. causing dieback in Pandanus tectorius plants. Whether plants are Australian or (1977). ‘Weeds of Queensland’, p. 464. var. pedunculus (A.Br.) Domin on the foreign matters much less than whether (Queensland Government Printer, Bris- Sunshine and Gold Coasts in Southeast they are invasive or benign. bane). Queensland. General and Applied Ento- Kloot, P.M. (1985). The spread of native mology 29, 11-20. 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(In press). ‘The new nature: win- vanced Education, Canberra). ners and losers in wild Australia’. (Pen- Garnett, S.T. and Crowley, G.M. (1997). guin, Melbourne). The golden-shouldered parrot of Cape Macdonald, D. (1887). ‘Gum boughs and York Peninsula: the importance of cups wattle bloom, gathered on Australian of tea to effective conservation. In ‘Con- hills and plains’, p. 198. (Cassell, Lon- servation outside nature reserves’, eds don). P. Hale and D. Lamb, p. 201. (Centre for Mack, R.N. (1991). The commercial seed Conservation Biology, University of trade: an early disperser of weeds in the Queensland, Brisbane). United States. Economic Botany 45, Garnett, S.T. and Crowley, G.M. (2000). 257-73. ‘The action plan for Australian birds McIntyre, S. and Barrett, S.C.H. (1985). A 2000.’ (Environment Australia, Can- comparison of weed communities of berra). rice in Australia and California. Pro- Grey, M. and Michael, P.W. (1986). 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