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Golden thistle (Scolymus hispanicus)

Golden thistle forms dense, spiny clumps that reduce grazing land and can injure livestock if eaten. It can also contaminate wool and provide cover for feral animals such as rabbits.

Key facts

Type: Weed, herb.

Native to: Mediterranean and Europe.

Established in: NSW, VIC.

Other names: Spanish Salsify, Spanish Oyster Plant, Sunnariah, Common Goldenthistle.

Best time to act: Seeds germinate in autumn, winter and spring; look for flowering in late spring and summer, and treat with herbicide when plants are in the rosette stage.

Identification

  • This upright, branching perennial herb grows up to 90 cm tall and has multiple slender stems growing from a crown.
  • Its robust, parsnip-like taproot can extend 60 cm into the soil.
  • Stem leaves are spiny and deeply divided, with spiny wings along the stems; less spiny rosette leaves form a radial cluster at the base.
  • The leaves have lighter-coloured veins, and broken stems, leaves and roots produce milky sap.
  • Golden-yellow flower heads, 2.5 to 4 cm across, grow on very short stalks in leaf axils and are surrounded by stout, spiny bracts.
  • Look-alike: Spotted Thistle (Scolymus maculatus) is similar, but it is an annual rather than a perennial and has white, bony thickened margins on its leaves and stem wings.

Where it grows

In Australia it occurs in Victoria and New South Wales, with major infestations around the Loddon River in north-central Victoria and records from parts of central and southern Victoria and south-western and central NSW.

Why it matters

  • The numerous spines can damage the mouths of livestock if the plants are eaten.
  • Dead plant material and seeds can contaminate wool.
  • Dense, impenetrable clumps exclude stock and other activities, reducing grazing land.
  • The clumps provide cover for feral animals such as rabbits, which can compete with native wildlife, damage native vegetation and contribute to soil erosion.

How it spreads

  • The brittle above-ground plant can break off at the base and tumble along the ground in the wind, shaking out seeds as it moves.
  • Sheep and other livestock can carry seeds in their wool and fur.
  • Tubers can spread when transported, including on cultivation machinery such as ploughs.

Control options

  • For small infestations, manually remove the whole plant, especially the tuber.
  • For larger infestations or difficult terrain, herbicide can be effective when used in the rosette stage as part of a two-year program; use registered herbicides according to approved directions.
  • Ploughing can be effective if repeated several times, but clean all machinery used so tubers are not carried to clean sites.
  • Slashing or mowing is not effective because above-ground growth can regrow from the tuber.

Hygiene and washdown

  • Clean cultivation machinery thoroughly after use because tubers can hitchhike to uninfested sites.
  • Be aware that seeds can also be carried in livestock wool and fur.
  • 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: Regionally prohibited / regionally controlled / restricted weed (varies by region). Where it is regionally prohibited, landowners must take all reasonable steps to eradicate it on their land. Where it is regionally controlled, landowners must take all reasonable steps to prevent its growth and spread on their land. Where it is a restricted weed, trade in it (including the plant, its seed or contaminated material) is prohibited.
  • 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.

  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria

Sources