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Saffron thistle (Carthamus lanatus)

Saffron thistle is widespread in Australia and competes with cereal crops, while also establishing in degraded pastures and rangelands. Its spiny growth restricts stock movement, and its seeds and heads reduce wool quality and can contaminate grain.

Key facts

Type: Weed, herb.

Native to: Europe, the Mediterranean region and western Asia.

Established in: QLD, NSW, ACT, VIC, TAS, SA, WA, NT.

Other names: Distaff Thistle, False Star Thistle, Woolly Safflower, Woolly Star Thistle.

Best time to act: Look for seedlings and rosettes after autumn or early-winter germination, and aim to prevent seed production before flowering in November or early December.

Identification

  • This is a stiff, spiny annual herb that grows to about 1 metre tall, usually with one ribbed stem and many branches in its upper half.
  • Its leaves have no stalk and clasp the stem; the lower rosette leaves are deeply divided, while the smaller, rigid stem leaves have many stout spines.
  • Yellow to cream-yellow flower heads grow singly at branch ends in dense clusters and are surrounded by rigid, spine-tipped bracts.
  • The pale to brownish-grey seeds are 3 to 8 mm long and may have a tuft of stiff bristles at the tip.
  • Look-alike: Toothed thistle and glaucous star thistle have pale violet to pinkish-purple flowers, unlike the yellow flowers of saffron thistle.
  • Look-alike: Safflower has bright orange to yellow flowers and mostly entire leaves, while saffron thistle has deeply divided leaves; glaucous star thistle also has a white to greyish bloom on its stems.

Where it grows

Across Australia it occurs in cultivated paddocks, poor pastures, rangelands, roadsides and neglected or disturbed areas, especially in low-fertility areas receiving 300 to 600 mm of annual rainfall.

Why it matters

  • It competes with cereal crops and reduces yields, and its hard stems increase wear and tear on harvesting machinery.
  • Sharp spines can restrict stock movement and injure grazing animals, particularly around the eyes and mouth.
  • Seeds and flower heads cause vegetable fault in wool, reducing its quality, and seeds can contaminate wheat.
  • It can invade degraded open native vegetation and grassy areas, but does not normally invade healthy, dense vegetation.

How it spreads

  • Seeds are not normally dispersed by wind and usually fall close to the parent plant.
  • Stiff seed bristles help seeds attach to clothing, wool and fur; dried heads can also tangle in sheep's wool.
  • Seed can be moved in soil or mud on vehicles and machinery, along roadsides by graders, and in agricultural produce such as harvested grain.

Control options

  • Use registered herbicides; spot-spray small patches and boom-spray larger areas, bearing in mind that plants at different growth stages can make control difficult.
  • For small populations that are newly established in an area, remove plants by hand or chip them out.
  • Deep ploughing to bury seeds below 10 to 15 cm is a starting point; shallow cultivation can destroy seedlings that emerge afterwards.
  • Mow, cut or slash just before flowering to prevent seed production, and use a rotation of 2 to 3 years of cropping followed by pasture.

Hygiene and washdown

  • Maintain good weed hygiene on vehicles and machinery, because seed-bearing soil or mud can be carried on them.
  • Seed bristles can attach to clothing, wool and fur, and dried seed heads can tangle in sheep's wool.
  • 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 controlled / restricted weed (varies by region). 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: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • Northern Territory: Declared weed, Class B. Class B: growth and spread must be controlled. All declared weeds are also Class C, so they must not be brought into the NT.
  • Australian Capital Territory: Declared pest. It is a declared pest throughout the ACT.

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
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • 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
  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources