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Artichoke thistle (Cynara cardunculus)

Artichoke thistle is a serious weed of permanent pastures, where dense infestations crowd out desirable plants and restrict stock movement. It can also invade grasslands, open woodlands and other natural areas, smothering native ground plants.

Key facts

Type: Weed, herb.

Native to: Mediterranean region of southern Europe and northern Africa.

Established in: NSW, VIC, TAS, SA, WA.

Other names: Cardoon, Wild artichoke, Desert artichoke, Spanish artichoke.

Best time to act: Plants flower from November to February, and herbicide treatment is recommended from September to November while plants are in the rosette or early flower-head stage.

Identification

  • It is an upright, long-lived herb, usually 60–150 cm tall, with a stout, often branched stem.
  • Its large, deeply divided leaves are greyish green, woolly underneath, and have sharp yellowish-orange spines along their edges and tips.
  • Large blue, pink or purple flower heads grow at the ends of branches; their bracts taper to stout, flattened spines.
  • The 6–8 mm seeds are topped with feathery hairs about 25–40 mm long.
  • Look-alike: Globe artichoke is a cultivated form with spineless bracts and generally lacks the spines of artichoke thistle.
  • Look-alike: Variegated thistle has variegated leaves and flower-head bracts ending in long, narrow spines, unlike the greyish-green leaves and short, stout spines of artichoke thistle.

Where it grows

In Australia it is widespread in the south and east, especially in Victoria and southern South Australia, and occurs in pastures, crops, grasslands, open woodlands, roadsides, gardens and disturbed sites.

Why it matters

  • Dense infestations outcompete and smother desirable pasture plants by drawing moisture and nutrients from the soil.
  • Spiny plants deter grazing and can restrict stock movement; hungry animals may eat the leaves, which have low nutrient value and may cause stomach impaction or mechanical injuries.
  • It can smother native ground plants in grasslands, open woodlands, and wetlands and riparian areas in drier regions.
  • It can invade gardens and disturbed sites, and is reported to cause dermatitis in some people.

How it spreads

  • Seeds are dispersed by wind, usually falling within a few metres, though they can travel up to 20 m from the parent plant.
  • Seeds also spread by animals, water, vehicles, mud, dumped garden waste and cut flower arrangements.
  • Established plants regrow each year from an underground crown and taproot; pieces of cut root can produce new plants where roots are disturbed.

Control options

  • Spot or boom spraying is described as effective during autumn and winter and usually needs to be done twice.
  • For small infestations, physically grub plants out and take care to remove most of the taproot.
  • Cultivation may need repeating for two or three years, followed by sowing pasture; grazing by goats can reduce flowering and seed production.

Hygiene and washdown

  • Seeds can spread in mud and on vehicles, so take care not to carry mud from infested sites.
  • 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: Declared plant. Depending on the declaration, it can be an offence to move it on public roads or sell it, and landowners may be required to control it on their land.
  • 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.

  • 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
  • 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