Quick Facts

Quick facts

• Groundsel Bush (Baccharis halimifolia) is a densely branching shrub that is usually up to 3 m.
• It is native to south-eastern USA and occurs from Gladstone in Queensland along the coast to northern New South Wales.
• Groundsel Bush is able to invade native littoral vegetation as well as being able to seriously degrade agricultural land.
• It is tolerant of a wide range of soil pH (alkalinity or acidity) and salinity.
• It has the ability to resprout from rootstock.
• Mature female plants are able to produce up to one million seeds.
• Seeds able to be spread by wind for several kilometres. Buried seeds have capacity to survive for over 2 years.

What Does It Look Like?

What is it?

Groundsel Bush is a densely branching shrub that is usually up to 3 m (occasionally to 6 m) tall. The bark of mature plants is deeply fissured. Younger stems are finely but prominently ribbed. Leaves are alternate, wedge- or kite-shaped, 2.5-7 cm long and 1-4 cm wide, and usually have about 2-4 prominent teeth in the upper half. The leaves are hairless on both surfaces.

Flower heads are usually crowded near branch-tips. Male and female flowers are produced on separate plants. Male flowers occur in heads that are 3-4 mm diameter, with 2-4 rows of greenish bracts 1-3 mm long. Female heads are similar but slightly larger, with bracts often purplish and up to 5 mm long. Flowering occurs mainly during autumn.

Female heads soon become fluffy-white as the seed bristles (pappus) on the developing seed elongate, to about 15 mm long at maturity. In cooler parts of its native habitat, plants are winter-deciduous, but this attribute has not been observed in Australia (Parsons & Cuthbertson 1992; Walsh 2007, pers. comm.).

For further information and assistance with identification of Groundsel Bush contact the herbarium in your state or territory.

Flower colour

Yellow, White

Growth form (weed type/habit)

Shrub

Where it currently grows? Preferred habitat

The preferred environment of Groundsel Bush appears to be margins of freshwater or saltwater swamps, estuaries or canals, but it is also able to colonise overgrazed pastures and other degraded land. It is capable of tolerating a wide range of soil salinity and pH (alkalinity or acidity) (Parsons & Cuthbertson 1992).

Are there similar species?

Members of the native genera Blumea and Pluchea are superficially similar to Groundsel Bush, but neither have male and female flowers on separate plants, nor do they grow as tall as Groundsel Bush (Walsh 2007, pers. comm.).

Why Is It A Weed?

What are its impacts?

Agriculture: In agricultural situations, Groundsel Bush successfully competes with pasture species and without early eradication will rapidly reduce productivity and become difficult to control. In native vegetation it establishes in freshwater and estuarine littoral shrublands (e.g. those dominated by Melaleuca, Avicennia marina, Casuarina glauca and adjacent eucalypt-dominated and/or rainforest communities) (Parsons & Cuthbertson 1992; National Herbarium of Victoria 2007).

It is reported to kill cattle, sheep and chickens if consumed (Parsons & Cuthbertson 1992).

Native ecosystems: Groundsel Bus 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) (Biosecurity Queensland 2016). 

Human: The wind dispersed seed can be a nuisance in urban areas where it sticks to insect screens and germinates in home gardens. Urban problems include potential allergies caused by air-borne pollen and the air-borne seed 'fluff' (pappus) (Land Protection 2007).

How does it spread?

Seeds of Groundsel Bush are wind-dispersed aided by the well-developed, persistent pappus (a tuft of silky hairs). It has been suggested that seeds may be spread for many kilometres in strong winds and that mature plants may produce up to one million seeds (Land Protection 2007). Seeds may also be dispersed by water, on vehicles and other machinery. They may remain dormant in the soil for at least 2 years (Panetta 1979).

What is its history in Australia?

Groundsel Bush was introduced into Western Australia in the mid 1800s and became established in the Busselton area, but was successfully eliminated from that area and no longer persists in Western Australia. It was introduced into the Brisbane area as an ornamental plant at a similar time, but by 1888 was reported to have become naturalised, north and south from Brisbane (Parsons & Cuthbertson 1992).

How To Manage It?

Best practice management

Recommended control methods involve hand removal of small plants; maintaining healthy pasture so that establishment niches are unavailable; burning or cutting plants and either painting stumps or spraying regrowth with a range of registered herbicides. Plants regenerate from rootstocks, so burning or cutting plants alone is usually insufficient to achieve control (Land Protection 2007).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

Non-chemical control: Groundsel Bush has also been recognised as a target for biological control through a cross-jurisdictional government process. This allows activities to be undertaken to develop effective biological controls. A range of insect biological control agents have been tried and six of these have established and offer some control: Stem Borer (Megacyllene mellyi), Plume Moth (Oidaematophorus balanotes), Gall Fly (Rhopalomyia californica), Groundsel Bush Leaf Beetle (Trirhabda baccharidis), Leaf Skeletoniser (Aristotelia ivae) and a Leaf Miner (Buccalatrix iveila). The Groundsel Bush Rust (Puccinia evadens) has more recently been established amongst populations of Groundsel Bush in Queensland (Land Protection 2007).

Does it have a biological control agent?

YES

When does it grow? (lifecycle/growth calendar)

Groundsel Bush seeds germinate whenever moisture conditions are favourable but the main germination period is from July to October following rain. Growth rates are slow following germination but increase during the summer. Plants of Groundsel Bush become reproductive in or after their second year of growth. Plants flower from December to April with the male plants flowering first and continuing after the female plants have finished. Seeds mature in April and May (Parsons & Cuthbertson 1992: Walsh 2007 pers. comm.).

Where Is It Found?

Which states and territories is it found?

NSW, WA, QLD

What areas within states and territories is it found?

Groundsel Bush occurs from near Gladstone in Queensland to the North Coast area of New South Wales, with an isolated occurrence in the Central Coast area. Most occurrences are within about 100 km of the coast, but extending to nearly 300 km inland near Taroom in Queensland (Parsons & Cuthbertson 1992; AVH 2007).

Also naturalised in Europe and New Zealand.

Where does it originate?

Groundsel Bush is native to south-eastern United States along the Atlantic and Gulf of Mexico coasts (from Massachusetts to Mexico) and also in the West Indies (Parsons & Cuthbertson 1992).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NSW, NT, QLD, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Baccharis halimifolia

Other scientific names (synonyms)?

Baccharis viminea DC. (misapplied by Hnatiuk, R.J. 1990, Census of Australian Vascular Plants. 42.)

Does it have other known common name(s)?

Consumption Weed, Groundsel, Groundsel Baccharis, Groundsel Tree