Rigid and winged by the continuation of the leaf bases. Flowering period is from July to September.
Seeds are tan with white and brown mottling.
Fruit of the marginal flowers dark colored and without bristles, inner fruits lighter in color with a terminal tuft of white-silvery bristles. Yellow starthistle is a bushy annual or sometimes biennial. It is covered with loose white cottony wool. It spreads by seeds that can remain dormant for 10 years. Seedflies and weevils are being used, but an effective control is many years away.