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White ball acacia (Acaciella angustissima)

White ball acacia has naturalised at scattered sites in Queensland, often near former trial plots or garden plantings. Its prolific seed production, persistent soil seed bank and ability to form dense thickets make it a potential threat to pasture and native vegetation.

Key facts

Type: Weed, shrub.

Native to: Subtropical and tropical America.

Established in: QLD.

Other names: Fern acacia, Prairie acacia, Prairie wattle, White-ball acacia.

Best time to act: Look for plants throughout the year, as flowering occurs year-round; follow-up checks are important because seeds can persist in the soil.

Identification

  • A thornless shrub or small tree, usually 2–7 m tall, with a short trunk.
  • Its leaves are finely divided and bipinnate, usually with 10–17 pairs of pinnae and many pairs of narrow leaflets.
  • Whitish, round or oval flower clusters are about 1–1.5 cm across.
  • Flat, papery pods are 3–9 cm long, green when immature and coffee-brown when ripe; each contains 8–12 small, round seeds.
  • Look-alike: Acaciella villosa and Acaciella glauca have a similar habit and can be confused with white ball acacia.

Where it grows

In Queensland it has been recorded at scattered eastern sites, including disturbed open woodlands, dry scrub and riparian habitats, as well as near former trial sites and garden plantings.

Why it matters

  • It can colonise gaps in open woodland and dry scrub and form dense thickets.
  • Thickets can exclude more desirable pasture plants and native vegetation.
  • Its hard-coated seeds can persist for many years in the soil, making eradication prolonged.
  • It has been observed spreading from cultivation into nearby riparian habitats and disturbed sites.

How it spreads

  • Plants produce large numbers of seeds, and hard-coated seeds can survive for many years in the soil.
  • It has naturalised near former trial plots and garden plantings, and can spread into nearby disturbed habitats.

Control options

  • For isolated plants, use an approved physical removal method where feasible, taking care to contain seed-bearing material.
  • If using herbicide, choose a product registered for the use and follow its label and local biosecurity advice.
  • Check treated sites repeatedly and deal with regrowth and new seedlings; long-term follow-up is needed to exhaust the soil seed bank.
  • Report suspected plants to the relevant state biosecurity agency for local advice.

Hygiene and washdown

  • Clean soil and plant material from vehicles, machinery, boots and equipment before leaving an infested site.
  • Avoid moving soil or seed-bearing plant material from known infestations.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Restricted matter, categories 2, 3, 4, 5. Report it to Biosecurity Queensland within 24 hours; do not give it away, sell or release it into the environment; do not move it; do not keep it. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Declared pest (C1), prohibited. C1 Exclusion: to be kept out of WA, or out of the parts of WA where it is not established. Report any sighting to DPIRD. It must not be brought into WA (prohibited organism).
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)

Sources