Winter annual. Leaves alternate, deeply lobed with spiny margins. Leaf base rounded and clasps the stem. Stems smooth on the lower portion but with stalked, glandular hairs on the upper portion. Yellow flowers in clusters at top of plant. Leaves and stems exude a "milky" juice when broken. Reproduces by seed. Found throughout the United States, north into Alaska and Yukon. Also found in the West Indies, South America, Eurasia, Africa and Hawaii. Annual sowthistle is similar but with sharply-pointed, clasping leaf base.