Perennial Thistle

Cirsium arvense

Alternative Name(s): Californian Thistle, Canada Thistle, Creeping Thistle

Family: Asteraceae.

Form: Herb

Origin: Native of Europe, northern Africa and Asia.

Flowers/Seedhead: Many small flowers (florets) in heads 1.5–2.5 cm long; petals 12–18 mm long; female flowers scented. Flowers summer and autumn.

Description: Erect perennial thistle to 1 (rarely to 1.5) m high. Stems ridged, smooth, hairless to slightly hairy. Leaves lanceolate in outline, upper surface dark green and variably hairy, lower surface white woolly to hairless; basal leaves in a rosette, leaves to 15 cm long and to 4 cm wide, margins wavy to toothed, narrowing to the base; stem leaves to 7 cm long, lobed, not on a stalk and base continuing down stems for a short distance. Seeds light brown to olive, smooth, finely longitudinally grooved.

Distinguishing features: Distinguished by creeping roots; spiny leaves; flowerheads 0.7–2.0 cm wide in panicles; florets all tubular, mauve, arising from a receptacle with bristle-like scales, male and female flowers on separate plants; bracts around heads soft, tips gradually pointed to short spined; seeds 2.5–4 mm long, compressed, topped by bristles 20–25 mm long.

Dispersal: Spreads by seed and creeping roots.