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Meadow knapweed (Centaurea moncktonii)

Meadow knapweed invades pastures, crops and natural areas in Australia, where it outcompetes pasture plants and is difficult to control. It is listed as prohibited matter in NSW and must be reported if found.

Key facts

Type: Weed, herb.

Native to: Europe; knapweeds mostly originate there..

Established in: NSW, VIC, TAS, SA.

Other names: Black knapweed.

Best time to act: Check regularly, especially after rain, and look for actively growing plants from September to May, when the listed glyphosate option is used.

Identification

  • A slender, upright, branched perennial herb that can grow to 1 m tall, with rough, hairy, ribbed stems.
  • The basal rosette leaves are green, oval-shaped or lobed, soft and finely hairy to velvety, and up to 25 cm long; stem leaves are green, about 3 cm long, stalkless and alternate.
  • Pink to purple flowers are about 15 mm in diameter and sit at stem tips that thicken just below the flower.
  • The flowerhead is surrounded by dark-brown to golden-brown bracts with fine, comb-like edges, giving it a small pine-cone appearance; the plant has no spines.
  • Look-alike: It resembles thistles, but knapweeds do not have sharp spines on their leaves; report spineless plants with pink-purple flowers in NSW.
  • Look-alike: Creeping knapweed can have deeply lobed leaves but lacks dark-brown or black bract tips, while spotted knapweed usually has deeply lobed leaves and dark-tipped bracts.

Where it grows

In NSW it has been found at Tenterfield in the Northern Tablelands, and it grows in most soil types, especially disturbed, moist sites such as overgrazed or cultivated paddocks, roadsides and creek lines where annual rainfall exceeds 750 mm.

Why it matters

  • It invades pastures, crops and natural areas and outcompetes pasture plants.
  • It produces chemicals that suppress other plants.
  • Stock do not usually eat it, and it is difficult to control.

How it spreads

  • Plants can produce 1,000 to 18,000 seeds each year; seeds germinate in autumn and overwinter as rosettes.
  • Seeds stick to animals and clothing and can also spread by water, wind, vehicles, contaminated soil and in manure.
  • Root fragments can grow into plants and spread by machinery or in soil or water.

Control options

  • Do not attempt to treat or dispose of this weed yourself; report any sighting in NSW immediately to the NSW Biosecurity Helpline on 1800 680 244.
  • NSW DPIRD, Agriculture and Biosecurity will lead the initial response for treatment and disposal.
  • Herbicide options listed include glyphosate for actively growing plants and Vigilant II applied by leaf wiping to rosette leaves; read and follow the product label and any permit conditions.
  • A follow-up treatment may be necessary after glyphosate treatment.

Hygiene and washdown

  • Seeds can stick to clothing and spread on vehicles, while root fragments can spread on machinery; check clothing, vehicles and machinery for plant material.
  • Avoid moving contaminated soil, plant material or water, which can carry seeds or root fragments.
  • 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: Prohibited matter. It is an offence to deal with it, and you must notify NSW DPIRD as soon as you become aware of it.
  • 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: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • 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.

  • 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

Sources