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Coastal silver oak (Brachylaena discolor)

Coastal silver oak is an introduced tree that can escape cultivation and establish in Australian coastal areas. Where it spreads into bushland, it can compete with native plants and change the structure of vegetation.

Key facts

Type: Weed, tree.

Native to: Coastal eastern and southern Africa, including South Africa.

Established in: .

Other names: Silver oak, Coast silver oak.

Best time to act: Search for plants when they are flowering or fruiting, and treat them before the fruits mature and disperse.

Identification

  • It is an evergreen shrub or small tree with a greyish, often rough trunk.
  • The leaves are simple and arranged alternately along the branches.
  • Leaves are usually dark green above and noticeably pale or silvery, with a fine covering of hairs, underneath.
  • Small, pale flower heads occur in clusters; male and female flowers are borne on separate plants.
  • The small dry fruits have a tuft of hairs that can carry them on the wind.
  • Look-alike: It may be confused with native trees or shrubs that have pale leaf undersides; check for the combination of alternate leaves, a silvery hairy underside and clustered flower heads.

Where it grows

In Australia, look for it in warm coastal districts, including disturbed sites, roadsides, gardens and bushland edges.

Why it matters

  • Established plants can compete with native vegetation for light and space.
  • Recruitment in bushland can make it harder for native plants to regenerate.
  • Dense growth may alter the structure of vegetation where the tree becomes established.

How it spreads

  • The fruits have hairs that help seeds disperse by wind.
  • It can escape from cultivation and establish beyond gardens.
  • Seeds or plant material may also be moved in contaminated soil or on equipment.

Control options

  • Hand-pull small seedlings and remove the root system where practical, taking care not to spread seed.
  • For larger plants, use an appropriate approved method such as cut-stump treatment with a herbicide registered for the situation, following the label and any local requirements.
  • Check treated sites for regrowth and new seedlings, and follow up until no further plants appear.
  • Report suspected infestations to the relevant state or territory biosecurity agency where reporting is required or recommended.

Hygiene and washdown

  • Clean soil, seeds and plant material from vehicles, machinery, boots and tools before leaving an infested site.
  • Avoid moving contaminated soil or plant waste to clean areas, and dispose of material in accordance with local guidance.
  • 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 3, 5. Do not give it away, sell or release it into the environment; 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: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • 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.

Sources