Click on images to enlarge

infestation (Photo: Sheldon Navie)

habit (Photo: Sheldon Navie)

habit of female plant in flower (Photo: Sheldon Navie)

habit of male plant in flower (Photo: Sheldon Navie)

lower leaves (Photo: Sheldon Navie)

upper leaves and old male flower-heads (Photo: Sheldon Navie)

young female flower-heads (Photo: Sheldon Navie)

old female flower-heads (Photo: Sheldon Navie)

masss of seeds with fluffy hairs (Photo: Sheldon Navie)

close-up of seeds (Photo: Steve Hurst at USDA PLANTS Database)

young plant (Photo: Sheldon Navie)

gall caused by the gall-fly biocontrol agent Rhopalomyia californica (Photo: Sheldon Navie)

damage caused by the plume moth biocontrol agent Oidaematophorus balanotes (Photo: Sheldon Navie)

Scientific Name

Baccharis halimifolia L.

Common Names

consumption weed, eastern baccharis, groundsel, groundsel baccharis, groundsel bush, groundsel tree, groundselbush, groundseltree, Sea Island myrtle, tree groundsel, waterbrush

Family

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

Control

Biosecurity Queensland Control Fact Sheet

Origin

Native to eastern USA (i.e. Connecticut, Massachusetts, New Jersey, Rhode Island, Oklahoma, Alabama, Arkansas, Florida, Georgia, Maryland, North Carolina, South Carolina and Texas) and the Caribbean.

Naturalised Distribution

A relatively widely naturalised species that is mostly found in eastern Australia. It is very common in south-eastern Queensland and north-eastern New South Wales, and is also present in other parts of these states (i.e. in central Queensland and in the coastal districts of central New South Wales). It was possibly also sparingly naturalised near Busselton in south-western Western Australia, but is no longer thought to be present in Western Australia.

Naturalised overseas in Europe and New Zealand.

Cultivation

This species is usually not deliberately cultivated any more, though it may occasionally be found in old gardens.

Habitat

A weed of open woodlands, forests, waste areas, disturbed sites, coastal canals, swampy areas, estuaries, mangrove wetlands, pastures, forestry plantations, orchards, plantation crops, irrigation channels, creek banks (i.e. riparian areas), parks, gardens, roadsides and urban bushland. It is mainly present in warmer temperate and sub-tropical climates.

Distinguishing Features

• an upright bushy shrub (1-3 m tall) with much-branched stems that become woody with age.
  
  
• its waxy leaves (2.5-7.0 cm long and 1-4 cm wide) have coarsely toothed margins.
  
  
• it produces separate male and female flower-heads on separate plants.
  
  
• the male flower-heads are cream to yellowish, while the female flower-heads are white and have a fluffy appearance.
  
  
• its straw-coloured or brown seeds (about 3 mm long) and are topped with a silky tuft of long white hairs (up to 12 mm long).

Habit

An upright (i.e. erect) and bushy shrub or small tree with many upward growing (i.e. ascending) branches. It usually grows 1-3 m tall, but occasionally reaches up to 7 m in height.

Stems and Leaves

The much-branched stems are hairless (i.e. glabrous), finely ribbed lengthwise (i.e. striate), and green when young. They turn brown, become woody, and eventually develop a deeply fissured bark as they mature.

The alternately arranged leaves are loosely diamond-shaped (i.e. rhomboid) to egg-shaped in outline (i.e. ovate) and have coarsely toothed (i.e. crenate) margins. These leaves (2.5-7 cm long and 1-4 cm wide) are borne on stalks (i.e. petioles) up to 15 mm long and have a waxy texture. They are hairless (i.e. glabrous) and can have either pointed or rounded tips (i.e. acute or obtuse apices). Leaves tend to be light green when young and turn a dull green colour as they mature, and the upper leaves tend to be smaller and less toothed or even have entire margins.

Flowers and Fruit

Separate male and female (i.e. unisexual) flower-heads (i.e. capitula) are borne on separate plants (i.e. this species is dioecious). The male (i.e. staminate) flower-heads (about 3 mm across) are cream to yellowish in colour, while the female (i.e. pistillate) flower-heads (3-5 mm across) are white and tend to mature after the male flower-heads. These flower-heads (i.e. capitula) not not have any 'petals' (i.e. ray florets) and their bases are enclosed in a few layers (i.e. involucre) of green bracts. Both types of flower-heads are grouped in branched clusters at the tips of the stems (i.e. in terminal panicles). Flowering occurs mainly during autumn.

The 'seeds' (i.e. achenes) are straw-coloured to brown in colour and hairless (i.e. glabrous). These 'seeds' (1.1-1.7 mm long) have 8-10 lengthwise (i.e. longitudinal) ribs and are topped with a silky tuft (i.e. pappus) of long white hairs (6-12 mm long).

Reproduction and Dispersal

The female plants produce large numbers of light fluffy seeds. These seeds are blown large distances by the wind and float on water. They may also be dispersed by animals, vehicles, machinery, and in contaminated agricultural produce (e.g. fodder).

Impacts

Groundsel bush (Baccharis halimifolia) is regarded as a significant environmental weed in Queensland and New South Wales. During a recent study it was listed as the second most important invasive plant species in south-eastern Queensland. It also rated highly in a survey of the most important environmental weeds of the New South Wales North Coast region. It is actively managed by community groups in Queensland and is also currently listed as a priority environmental weed in two Natural Resource Management regions.

This species is of most concern in sub-tropical melaleuca wetlands, where it can form a dense understorey that suppresses the growth of native sedges and interferes with the natural ecosystem. It can also become abundant in native vegetation along watercourses and in coastal woodlands and forests. Conservation areas are also under threat from invasion by this species, and it has invaded several reserves in Queensland (e.g. Noosa National Park, Maroochy River Conservation Park and Pimpama River Conservation Area) and New South Wales (e.g. Ballina Nature Reserve, Wooyung Nature Reserve and Cullendulla National Park).

Other Impacts

Groundsel bush (Baccharis halimifolia) will rapidly colonise overgrazed pastures and competes with pasture species for water and nutrients. Thick stands can inhibit the movement of livestock and reduce the productivity and carrying capacity of pastures. The air-borne pollen, which is produced in massive quantities for a short period of the year, is suspected of causing allergies in humans. The seed 'fluff'can also be a nuisance in urban areas, where it sticks to insect screens and accumulates in other areas.

Legislation

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

• New South Wales: Class 3 - a regionally controlled weed. The relevant local control authority must be promptly notified of the presence of this weed and it must be fully and continuously suppressed and destroyed (in a large number of local authority areas). See the New South Wales Department of Primary Industries Noxious Weeds List at http://www.dpi.nsw.gov.au  for more detailed information on which local areas are covered in these declarations.
  
  
• Northern Territory: C - not to be introduced into the Territory.
  
  
• Queensland: Class 2 - landowners must take all reasonable steps to keep land free of this species (throughout the entire state). It is also illegal to sell a declared plant or its seed in this state.
  
  
• Western Australia: Prohibited - on the prohibited species list and not permitted entry into the state.

Management

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

• the Biosecurity Queensland Fact Sheet on this species, which is available online at http://www.dpi.qld.gov.au.
  
  
• the New South Wales Department of Primary Industries Agfact on this species, which is available online at http://www.dpi.nsw.gov.au.
  
  
• the Northern Territory Department of Natural Resources, Environment and The Arts Agnote on this species, which is available online at http://www.nt.gov.au/weeds.

Sources

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 (2006). Baccharis halimifolia L., Asteraceae. Pacific Island Ecosystems at Risk (PIER): plant threats to Pacific ecosystems. http://www.hear.org/pier/species/baccharis_halimifolia.htm. Institute of Pacific Islands Forestry, Hawaii, USA.

Anonymous (2006). Declared Plants of Queensland. Natural Resources and Water Facts - pest series, PP1. The State of Queensland (Department of Natural Resources and Water), Brisbane, Queensland.

Anonymous (2006). Germplasm Resources Information Network (GRIN). http://www.ars-grin.gov/cgi-bin/npgs/html/index.pl. National Germplasm Resources Laboratory, National Genetic Resources Program, Agricultural Research Service (ARS), United States Department of Agriculture (USDA), Beltsville, Maryland, USA.

Anonymous (2006). Groundsel bush. Baccharis halimifolia. Natural Resources and Water Facts - pest series, PP13. 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). 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, Tasmania.

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

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.

Ensbey, R. (2001). Groundsel Bush. Agfacts. Agfact P7.6.35, second edition 2001. NSW Agriculture, Orange, New South Wales.

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

Keighery, G. and Longman, V. (2004). The naturalized vascular plants of Western Australia. 1: checklist, environmental weeds and distribution in IBRA regions. Plant Protection Quarterly 19: 12-32.

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

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, Queensland.

Newbould, S. (2001). Groundsel Bush (Baccharis halimifolia). Agnote. Weeds Branch, Primary Industry and Fisheries, Northern Territory of Australia, Katherine, Northern Territory.

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

Porteners, M.F. (1992). Baccharis halimifolia L. 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.

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