A genus of annual or perennial herbs which have simple leaves arranged in a spiral along the stem. The flower heads are usually held in clusters or corymbs. The central florets are bisexual and the outer ones female, with tubular, simple corollas. There are no broad petals in the ray florets. The achenes are usually softly hairy and compressed, with a simple row of pappus hairs. Many species are N. American weeds. There are about 50 species, found in temperate and subtropical regions.
Subjects: Plant Sciences and Forestry.