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Spotted thistle (Scolymus maculatus)

Spotted thistle is an introduced annual weed of pastures and wasteland, recorded in New South Wales and Queensland. Its spiny leaves and stems can make infested areas harder to use and manage.

Key facts

Type: Weed, herb.

Native to: Mediterranean region.

Established in: QLD, NSW.

Other names: Spotted golden thistle.

Best time to act: Look for rosettes before the recorded December flowering period and treat plants before they set seed.

Identification

  • It is an annual herb that grows up to 1 m high and is nearly hairless.
  • Young plants form a rosette of soft, lobed leaves; mature stem leaves are rigid, deeply lobed and spiny.
  • The leaf edges and the wings running along the stem are strongly thickened and white.
  • Yellow flower heads are borne singly or in clusters of two to four, and are 8–15 mm across.
  • It flowers in December; its achenes are 2.5–4 mm long and have no pappus.
  • Look-alike: It may be confused with other spiny thistles, including saffron thistle; look for the conspicuously thickened white leaf margins and stem wings to help distinguish it.

Where it grows

In Australia it grows as a weed of pastures and wasteland, recorded in New South Wales from the Kempsey area to Merriwa and also in Queensland.

Why it matters

  • The spiny foliage can make pasture less usable for grazing and make work in infested sites difficult.
  • Its prickly leaves and stems can be an obstacle for people and livestock moving through dense growth.
  • As an annual weed, it can compete with pasture and other vegetation while it is growing.

How it spreads

  • It reproduces by achenes, so preventing plants from setting seed is important.
  • Seeds may be moved with contaminated soil, fodder, vehicles or machinery.
  • Infestations can be extended when equipment or materials carrying seed are moved to clean areas.

Control options

  • For small infestations, wear gloves and pull or dig plants out before they set seed, then dispose of them so seed is not spread.
  • Where chemical control is appropriate, use only a herbicide registered for the weed and site, and follow its label and any local requirements.
  • Recheck treated areas and nearby ground, and control regrowth or new seedlings before they produce seed.
  • Check current local requirements and report new or suspected infestations to the relevant state or territory biosecurity agency.

Hygiene and washdown

  • Clean soil and plant material from boots, vehicles and machinery before leaving an infested area, and avoid carrying contaminated soil or fodder to clean sites.
  • Dispose of collected plants and contaminated material in a way that prevents seed from being spread.
  • 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: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • 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.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development

Sources