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Carthamus glaucus (Carthamus glaucus)

Australian records of glaucous star-thistle are uncertain, so a suspected plant should be identified carefully before it is treated or reported as this species. It is a spiny relative of cultivated safflower, and distinguishing it from other Carthamus species is important for reliable weed records and management.

Key facts

Type: Weed, herb.

Native to: Mediterranean region and western Asia.

Established in: .

Other names: glaucous carthamus.

Best time to act: Look for plants while they are growing and treat them before flowering and seed set.

Identification

  • Look for an upright, branching, thistle-like herb with blue-green, glaucous foliage.
  • Leaves are alternate and may have toothed or divided edges with sharp spines.
  • Flower heads are borne at the ends of stems and have yellow florets.
  • The enclosing bracts around each flower head are spiny.
  • Check mature seed heads and the whole plant when identifying it, as similar Carthamus species occur in Australia.
  • Look-alike: Other Carthamus species, including safflower (Carthamus tinctorius), can look similar; Australian records of C. glaucus have been questioned, with some specimens re-identified as C. leucocaulos.

Where it grows

Its occurrence in Australia is uncertain; check suspected plants in disturbed or agricultural sites against a reliable identification before recording them as this species.

Why it matters

  • Its weed impact in Australia is not established, and the identity of reported Australian specimens has been questioned.
  • The spiny foliage may make plants difficult to handle and may impede access where they occur.
  • Correct identification matters because other Carthamus species are naturalised in Australia and some are declared noxious in certain jurisdictions.

How it spreads

  • Seed may be moved unintentionally with soil, plant material, or equipment; avoid moving material from a suspected infestation.
  • Confirm the species and whether seed is present before transporting or disposing of plant material.

Control options

  • First confirm identification, preferably with a local botanist or herbarium, because Australian records of this species are uncertain.
  • For small, accessible plants, remove them before flowering and seed set, taking care to avoid contact with the spines; dispose of material according to local guidance.
  • If using herbicide, choose a product registered for the target plant and site, and follow its label and any local requirements.
  • Revisit the site to check for regrowth or new seedlings, and report a suspected occurrence to the relevant state or territory biosecurity agency where appropriate.

Hygiene and washdown

  • Before leaving a suspected site, remove soil and plant material from boots, tools, vehicles, and machinery, and avoid carrying contaminated material elsewhere.
  • Contain removed plants and any seed-bearing material during transport and dispose of them according to 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: 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: 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