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Plumeless thistle flowers
  • Winter annual or biennial

  • Spine covered thistle growing to 0.3 to 1.2 m tall

  • Introduced from Eurasia

Plumeless thistle leaves

Plumeless thistle
(Carduus acanthoides)

Quick Identification

  • Small reddish-purple flower heads

  • Stem leaves are only hairy on the upper side

  • Spiny wings densely covering stem up to base of flower heads

  • Narrow bracts below the seed head appear as sharp spines

Damages range and pasture productivity and reduces biodiversity.

Hand pulling or digging is effective if root crown is removed. Best done when soil is moist. Wear gloves to avoid skin contact.  If any portion of flower is beginning to emerge, or if seed heads are formed, pick, bag, and remove. Selective herbicides are effective.

Small reddish-purple flowers (less than 3 cm in diameter) are either solitary or in clusters of two to five. Narrow bracts below the seed head appear as sharp spines.

Leaves & Stems
Leaves have hair only on the underside, spines along the leaf margin, and a light coloured midrib. Stem leaves are stalkless and extend down the stem like spiny wings. The stems are branched near the top and are densely covered with spiny wings up to base of flower heads. Rosette leaves are deeply serrated nearly to the midrib.

Screenshot 2024-05-15 135419.jpg

Large, fleshy taproot.

Reproduction & Dispersal
Reproduces by seed only which disperses primarily by wind.  Plumeless thistles are extremely prolific seed producers with up to 9,000 seeds produced by a single plant.


Single seeded fruits are 2 to 3 mm long, light brown with faint longitudinal stripes, and have a plume (pappus) with bristles 11 to 12 mm long.

Preferred Habitat
Pastures, grasslands, crop fields, river valleys, roadsides and disturbed open sites.

Interesting Facts
Unpalatable to grazing animals.

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