[5][2] It is native to the Americas and has been introduced to Asia, Africa, the Pacific islands, and Australia.

[4] These are annual or perennial herbs with branching stems usually reaching 10 to 20 centimeters in length, growing prostrate or erect.

The oppositely arranged leaves are smooth-edged or toothed, and usually have rough or soft hairs.

The flower heads are usually solitary at the tips of the stem branches, or occasionally borne in inflorescences.

Some species lack ray florets, but some have 5 to 20 or more, usually in yellow or orange, but occasionally white or purple.