Sub-category: Aster family
A herbaceous perennial plant growing up to 150 cm, forming extensive clonal colonies from thickened roots that send up numerous erect shoots during the growing season. Stems 30 to 150 cm, slender green and freely branched, smooth and glabrous (having no trichomes or glaucousness), mostly without spiny wings. Leaves alternate on the stem with their base sessile and clasping or shortly decurrent. The leaves are very spiny, lobed, up to 15 to 20 cm long and 2 to 3 cm broad (smaller on the upper part of the flower stem). The inflorescence is 10 to 22 mm diameter, pink-purple, with all the florets of similar form (no division into disc and ray florets). The flowers are usually dioecious, but not invariably so, with some plants bearing hermaphrodite flowers. The seeds are 4 to 5 mm long, with a feathery pappus which assists in wind dispersal. 1 to 5 flower heads per branch, with plants in very favorable conditions producing up 100 heads per shoot. Each head contains an average of 100 florets.
The species is widely considered a weed even where it is native. Found in fields, meadows, roadsides, and waste areas.