Asteraceae

Cirsium arvense

Common Names: Perennial thistle

Plant Form: Perennial herb, spreading with rhizomes. Size: Up to 1 m tall. Stem: Green, smooth, sometimes hairy, with white spines. Leaves: Dark green above, white below, spiny, lobed, 1-7 cm long. Flowers: Purple, narrow, in heads with 8-15 mm diameter bracts in several series, with short spines at tips, sometimes hairy or cobwebby, grouped in large clusters. Fruit and Seeds: 3 mm long, smooth, with parachuting hairs 20-25 mm long. Habitat: Roadsides, pasture and cropping land. Distinguishing Features: Flowerheads narrowly cylindric and in large clusters, compared to wide, solitary or in small clusters in Spear thistle (Cirsium vulgare). Impacts: Decreases agricultural productivity by competing with crop species, can cause injury if grazed, and is a potential host for pests and diseases.