Spiny sowthistle Sonchus asper (L.) Hill
Family: Asteraceae (Composite family)
Life cycle: Annual
Native status: Introduced to N. America
Habitat: Waste areas
General description: Initially forms a basal rosette of leaves, the stem elongates into erect, unbranched plant. Leaves are glossy, variably lobed or toothed with prickly margins, with a rounded auricle clasping the stem. Stem emits a milky sap. Produces clusters of yellow composite flowers that have release seed attached to feathery pappus.
Key ID traits: Glossy leaves with rounded, clasping auricles.
Similar species: There are numerous wind-dispersed members of the Asteracea family that have similar growth habits that appear in disturbed habitats. Annual sowthistle is slightly taller than spiny sowthistle and has pointed auricles. Prickly lettuce has spines on underside of mid-vein.
Miscellaneous: The sowthistles are not aggressive plants, but frequently found in disturbed areas and the seedheads filled with pappus attract people’s attention.