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Scientific Name
Synonyms
Common Names
Family
Origin
Naturalised Distribution
Habitat
Distinguishing Features
Habit
Stems and Leaves
Flowers and Fruit
Reproduction and Dispersal
Impacts
Other Impacts
Control 
Similar Species
Legislation
Management
Sources
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Click on images to enlarge


infestation (Photo: Forest and Kim Starr, USGS)


habit in flower (Photo: Sheldon Navie)


the bright green, oppositely arranged, leaves (Photo: Sheldon Navie)


close-up of the relatively broad and almost triangular leaves (Photo: Sheldon Navie)


the branched flower clusters at the tips of the stems (Photo: Sheldon Navie)


the small white flower-heads are borne in dense clusters (Photo: Sheldon Navie)


close-up of the flower-heads, each with numerous tiny tubular flowers (Photo: Sheldon Navie)


close-up showing the greenish flower-head bracts and the sticky hairs on the young stems (Photo: Sheldon Navie)


older flower-heads and 'seeds' (Photo: Sheldon Navie)


seedling (Photo: Sheldon Navie)


comparison of crofton weed (Ageratina adenophora), left, and mistflower (Ageratina riparia), right (Photo: Sheldon Navie)

Crofton weed
Ageratina adenophora

Scientific Name

Ageratina adenophora (Spreng.) R.M. King & H. Rob.

Note: Eupatorium adenophorum Spreng. is currently used in Western Australia.

Synonyms

Eupatorium adenophorum Spreng.

Common Names

cat weed, catweed, crofton weed, croftonweed, hemp agrimony, Mexican devil, sticky agrimony, sticky eupatorium, sticky snakeroot, white thoroughwort

Family

Asteraceae (Queensland, New South Wales, the ACT, Victoria, Tasmania, Western Australia and the Northern Territory)
Compositae (South Australia)

Origin

Native to Mexico.

Naturalised Distribution

Widely naturalised in eastern Australia and also present in some parts of southern Australia. It is common in the coastal and sub-coastal districts of southern and central Queensland and eastern New South Wales, as far south as Wollongong, and is particularly abundant in the areas adjacent to the Queensland/New South Wales border. It is also common on Lord Howe Island, occasionally naturalised near Adelaide in south-eastern South Australia and near Perth in south-western Western Australia, and sparingly naturalised near Melbourne in southern Victoria.

Widely naturalised in many other parts of the world, including in southern Europe, Africa, Asia, New Zealand, south-western USA (i.e. California), French Polynesia, Fiji and Hawaii.

Habitat

This species is a weed of roadsides, railways, pastures, fence-lines, disturbed sites, waste areas and waterways in sub-tropical and warmer temperate regions. It it is also commonly found in urban bushland, open woodlands, forest margins, rainforest clearings and plantation crops (e.g. bananas and sugar cane).

Distinguishing Features

Habit

A long-lived (i.e. perennial) herbaceous plant or small soft-stemmed shrub usually growing 1-2 m tall, but occasionally reaching up to 3 m in height. It produces numerous upright (i.e. erect) stems from a woody rootstock.

Stems and Leaves

The branched stems are densely covered in sticky (i.e. glandular) hairs when young and may be green, reddish or purplish in colour. They become slightly woody and turn brownish-green or brown in colour when mature.

The leaves are oppositely arranged along the stems and are borne on stalks (i.e. petioles) 1-6 cm long. The leaf blades (4-15 cm long and 3-9 cm wide) are trowel-shaped, diamond-shaped (i.e. rhomboid), or triangular with bluntly or sharply toothed (i.e. crenate or serrate) margins. These leaves have sharply pointed tips (i.e. acute apices) and are mostly hairless (i.e. glabrous), but their stalks (i.e. petioles) are often covered in sticky hairs (i.e. they are glandular pubescent).

Flowers and Fruit

The small flower-heads (i.e. capitula) lack large 'petals' (i.e. ray florets) and consist of several tiny flowers (i.e. tubular florets) surrounded by two rows of greenish bracts (i.e. an involucre) 3-5 mm long. These flower-heads (5-8 mm across) are borne in large numbers and arranged in clusters at the tips of the branches (i.e. in terminal corymbose inflorescences). The tiny tubular florets (3-5 mm long) are white and contain both male and female flower parts (i.e. they are bisexual). Flowering occurs mostly during spring and early summer in northern regions, and during late summer and autumn in southern regions.

The 'seeds' (i.e. achenes) are slender, reddish-brown or blackish-brown in colour, and slightly curved. These 'seeds' (1-2 mm long and 0.3-0.5 mm wide) have four or five slight ribs which run lengthwise (i.e. longitudinally) and their bodies are hairless (i.e. glabrous). However, they are topped with a ring (i.e. pappus) of numerous whitish hairs (3-4 mm long), which are readily shed.

Reproduction and Dispersal

This plant reproduces mainly by seed. These seeds are easily dispersed by wind and float on water. They may also be spread in by animals and vehicles and can contaminate agricultural produce.

Impacts

Crofton weed (Ageratina adenophora) is regarded as a significant environmental weed in Queensland and New South Wales, and was recently listed as a priority environmental weed in four Natural Resource Management regions in these states. This species colonises forest margins, stream banks and disturbed areas, preferring shaded wetter areas but also growing in open sunny sites. It also thrives in damp areas such as wetland margins, drainage lines, gullies and in clearings in wetter forests. It grows in large dense clumps and will eventually out-compete all other plants in an area, choking out native vegetation and forming a monoculture.

In Queensland, crofton weed (Ageratina adenophora) is most prevalent in south-eastern parts of the state, where it invades pastures and colonises natural areas. It is a very significant environmental weed in south-eastern Queensland, where it was recently ranked among the top 20 most invasive plant species.

In New South Wales, crofton weed (Ageratina adenophora) is prominent as an environmental weed in the north coast region as well as on the central coast and in wider Sydney and Blue Mountains region. It is most common in northern New South Wales, but is also relatively common along the central coast and in the northern parts of the south coast. This species appears on several local environmental weed lists in the Sydney area (e.g. in Randwick City, Warringah Council and Sutherland Shire) and is one of the most common weeds in the Sutherland Shire, in southern Sydney. It also commonly invades State forests and National Parks in eastern New South Wales. Crofton weed (Ageratina adenophora) is also listed as a principal weed species in lowland rainforests in eastern New South Wales, an ecological community that has been given an endangered listing in this state.

Crofton weed (Ageratina adenophora) is also a weed of particular concern on Lord Howe Island. This species tends to locally dominate exposed sites, where it excludes native species. It occurs at many sites on the island, but is particularly apparent on exposed mountain slopes (e.g. on Mount Gower). It is considered to be having a serious impact on the World Heritage values of Lord Howe Island and threatening the survival of two endangered plant species on the island (i.e. Carmichaelia exsul and Calystegia affinis).

These are not the only rare native species to be threatened by crofton weed (Ageratina adenophora). Invasion of habitat by this weed is also seen as a threat to the vulnerable Hartman's sarcochilus (Sarcochilus hartmannii), an epiphytic orchid in north-eastern New South Wales, and the Border Ranges daisy (Brachyscome ascendens), and endangered species restricted to highland areas in south-eastern Queensland and north-eastern New South Wales. The endangered native jute (Corchorus cunninghamii) is also threatened by invasion of crofton weed (Ageratina adenophora) and other weed species at many of the locations where it is known to exist. The giant spear lily (Doryanthes palmeri) is another vulnerable native species from south-eastern Queensland and north-eastern New South Wales that is threatened by crofton weed (Ageratina adenophora). One study found that seedlings of this species that had begun to establish were soon out-competed by crofton weed (Ageratina adenophora), and that there were dense populations of this and other weed species in some of the sites were this species is found.

Other Impacts

Crofton weed (Ageratina adenophora) is also an aggressive weed in pastures in eastern Australia. It prefers wetter pastures (e.g. kikuyu grass pastures on wetter slopes), is usually not eaten by cattle, and can reduce the carrying capacity and productivity of invaded areas.

It is also poisonous to livestock, being particularly toxic to horses. In fact, this species is the cause of an acute pulmonary disease in horses which is known as "Tallebudgera horse disease" in Queensland and "Numinbah horse sickness" in New South Wales. This condition can be fatal if enough of the weed is consumed over a long period.

Control

Biosecurity Queensland Control Fact Sheet

Similar Species

Crofton weed (Ageratina adenophora) is very similar to mistflower (Ageratina riparia ), which is also known as 'creeping crofton weed', and relatively similar to Siam weed (Chromolaena odorata ) and Senegal tea plant (Gymnocoronis spilanthoides ). These species can be distinguished by the following differences:

Blue billygoat weed (Ageratum houstonianum ), billygoat weed (Ageratum conyzoides subsp. conyzoides) and praxelis (Praxelis clematidea ) are slightly similar when in the vegetative stages of growth, but usually have hairy leaves. They can be easily distinguished by their bluish, purplish or pinkish-coloured flower-heads.

Legislation

This species is declared under legislation in the following states and territories:

Management

For information on the management of this species see the following resources:

Sources

Anonymous (1999). Corchorus cunninghamii. Threatened Species Information. NSW National Parks and Wildlife Service, Hurstville, New South Wales.

Anonymous (2002). A Global Compendium of Weeds. http://www.hear.org/gcw. Hawaiian Ecosystems at Risk Project and Department of Agriculture - Western Australia.

Anonymous (2002). Australia's Virtual Herbarium. http://www.anbg.gov.au/avh. Australian National Botanic Gardens, Environment Australia, Canberra, ACT.

Anonymous (2003). Ageratina adenophora. Crofton weed. Weed Facts. Sutherland Shire Council, Sutherland, New South Wales.

Anonymous (2006). Ageratina adenophora (Spreng.) King & H.E. Robins. Sticky snakeroot. Plants Profile. http://plants.usda.gov/java/profile?symbol=AGAD2. Natural Resources Conservation Service, United States Department of Agriculture (USDA).

Anonymous (2006). Ageratina adenophora (Spreng.) R.M.King & H.Rob., Asteraceae. Pacific Island Ecosystems at Risk (PIER): plant threats to Pacific ecosystems. http://www.hear.org/pier/species/ageratina_adenophora.htm. Institute of Pacific Islands Forestry, Hawaii, USA.

Anonymous (2006). Crofton weed. Ageratina adenophora. Natural Resources and Water Facts - pest series, PP16. Land Protection, The State of Queensland (Department of Natural Resources and Mines), Brisbane, Queensland.

Anonymous (2006). National List of Naturalised Invasive and Potentially Invasive Garden Plants. Version 1.2. World Wildlife Fund - Australia (WWF Australia).

Anonymous (2007). Border Ranges Daisy - profile. Threatened Species. http://www.threatenedspecies.environment.nsw.gov.au/tsprofile/profile.aspx?id=10108. NSW National Parks and Wildlife Service, Department of Environment and Climate Change, Sydney, New South Wales.

Anonymous (2007). Hartman's Sarcochilus - profile. Threatened Species. http://www.threatenedspecies.environment.nsw.gov.au/tsprofile/profile.aspx?id=10745. NSW National Parks and Wildlife Service, Department of Environment and Climate Change, Sydney, New South Wales.

Anonymous (2007). NSW Department of Primary Industries. http://www.dpi.nsw.gov.au. NSW Department of Primary Industries, Orange, New South Wales.

Anonymous (2007). Weeds Australia. http://www.weeds.org.au. National Weeds Strategy Executive Committee, Launceston.

Auld, B.A. and Medd, R.W. (1996). Weeds: an illustrated botanical guide to weeds of Australia. Inkata Press, Sydney, NSW.

Auld, T.D. and Hutton, I. (2004). Conservation issues for the vascular flora of Lord Howe Island. Cunninghamia 8: 490-500.

Barker, B., Barker, R., Jessop, J. and Vonow, H. (2005). Census of South Australian Vascular Plants. Fifth Edition. The Botanic Gardens of Adelaide and State Herbarium, Government of South Australia, Adelaide, South Australia.

Batianoff, G.N. and Butler, D.W. (2002). Assessment of invasive naturalized plants in south-east Queensland. Plant Protection Quarterly 17: 27-34.

Bostock, P.D. and Holland, A.E. (2007). Census of the Queensland Flora 2007. Queensland Herbarium, Environmental Protection Agency (EPA), Brisbane, Queensland.

Coleman, H. (1997). *Eupatorium adenophorum Spreng. Crofton weed. FloraBase: The Western Australian Flora. http://florabase.calm.wa.gov.au. Western Australian Herbarium, Department of Conservation and Land Management (CALM), Perth, Western Australia.

Friend, E. (1983). Queensland Weed Seeds. Queensland Department of Primary Industries, Brisbane, Queensland.

Green, P. (1994). Flora of Australia, Volume 49, Oceania Islands 1. Australian Biological Resources Study and CSIRO Publishing, Canberra, ACT.

Henderson, L. (2001). Alien Weeds and Invasive Plants. Plant Protection Research Institute, Agricultural Research Council, South Africa.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds: a guide to the weeds of Western Australia. The Plant Protection Society of Western Australia, Victoria Park, Western Australia.

Kleinschmidt, H.E., Holland, A. and Simpson, P. (1996). Suburban Weeds. 3rd Edition. Department of Primary Industries, Brisbane, Queensland.

Lamp, C. and Collet, F. (1989). Field Guide to Weeds in Australia. Inkata Press, Melbourne, Victoria.

Lazarides, M., Cowley, K. and Hohnen, P. (1997). CSIRO Handbook of Australian Weeds. CSIRO Publishing, Collingwood, Victoria.

Navie, S.C. (2004). Declared Plants of Australia. CD-ROM. The University of Queensland, St. Lucia, Brisbane, Queensland.

Navie, S.C., Markwell, B., Playford, J. and Adkins, S.W. (2002). Suburban and Environmental Weeds: an interactive identification and information system. CD-ROM. The University of Queensland, St. Lucia, Brisbane, Queensland.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious Weeds of Australia. Inkata Press, Melbourne, Victoria.

Perry, D.A. (2001). The distribution, relative abundance and conservation status of Doryanthes palmeri (Doryanthaceae) in New South Wales. Cunninghamia 7: 183-193.

Porteners, M.F. (2007). Ageratina adenophora (Spreng.) R.M.King & H.Rob. New South Wales Flora Online. PlantNET - The Plant Information Network System of Botanic Gardens Trust. http://plantnet.rbgsyd.nsw.gov.au. Royal Botanic Gardens and Domain Trust, Sydney, New South Wales.

Roy, B., Popay, I., Champion, P., James, T. and Rahman, A. (1998). An Illustrated Guide to Common Weeds of New Zealand. New Zealand Plant Protection Society, Lincoln, New Zealand.

Scher, J. (2005). Federal Noxious Weed Disseminules of the U.S.: an interactive identification tool for seeds and fruit of plants on the United States federal noxious weed list. CD-ROM. Animal and Plant Health Inspection Service (APHIS), United States Department of Agriculture (USDA).

Stanley, T.E. and Ross, E.M. (1986). Flora of South-eastern Queensland. Volume 2. Department of Primary Industries, Brisbane, Queensland.

Trounce, B. and Dyason, R. (2003). Crofton weed. Agfacts. Agfact P7.6.36, 2nd edition (June 2003). NSW Agriculture.

Walsh, N.G. and Stajsic, V. (2007). A Census of the Vascular Plants of Victoria. Eighth Edition. National Herbarium of Victoria, South Yarra, Victoria.