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African thistle (Berkheya rigida)

African thistle is an introduced weed recorded in parts of southern Australia, where it can become locally abundant in sandy sites and pastures. It can form large colonies and is regarded as a minor or potential environmental weed in Victoria, Tasmania and Western Australia.

Key facts

Type: Weed, herb.

Native to: Southern Africa, including South Africa’s Cape Province.

Established in: VIC, TAS, SA, WA.

Other names: Berkheya, berkheya thistle, Augusta thistle, Hamelin thistle.

Best time to act: Find plants by checking for their distinctive spiny flower heads, and treat them while actively growing before they can spread further.

Identification

  • Look for a thistle-like herb with deeply lobed leaves and spiny margins.
  • Lower leaves are deeply lobed, while upper leaves occur around the flowering stems.
  • The flower heads have conspicuous spiny floral bracts.
  • Plants spread from creeping underground stems and can form large colonies.
  • Look-alike: It may be confused with other spiny thistles; check for the combination of deeply lobed lower leaves and flower heads surrounded by spiny bracts.

Where it grows

In Australia it grows in sandy sites and pastures, particularly in coastal districts, and has also been recorded in native vegetation in south-western Western Australia.

Why it matters

  • It can be locally abundant in coastal environments and pastures.
  • Creeping underground stems allow it to form large colonies.
  • It is regarded as a minor or potential environmental weed in Victoria, Tasmania and Western Australia.
  • It is listed as an environmental weed in the Mornington Peninsula Shire and has been recorded in reasonably intact native vegetation near Augusta in south-western Western Australia.

How it spreads

  • Creeping underground stems allow plants to spread and form colonies.
  • The species is thought to have been introduced from South Africa in ships’ ballast many years ago.
  • Australian infestations are mostly scattered, and the species is not yet widely distributed.

Control options

  • For small infestations, carefully dig out the plant, including its crown and underground stems; wear protective clothing because of the spiny leaves and flower heads.
  • Use only herbicides registered for the target weed and site, and follow the product label and local requirements.
  • Inspect treated areas for regrowth and follow up promptly; avoid spreading plant material or contaminated soil during removal.
  • Check with the relevant state or territory biosecurity agency for local advice and reporting requirements.

Hygiene and washdown

  • Clean soil and plant material from boots, tools and machinery before leaving an infested site.
  • Avoid moving contaminated soil or plant material to clean areas, and dispose of removed material responsibly.
  • 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: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. 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: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • Northern Territory: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • 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.

  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources