They are also a problem in prairies, old fields, and hay fields. The life cycles of these species are similar. They are primarily biennial or winter annuals, but may act as annuals in areas of sparse vegetation and fertile soil. Seedlings emerge from early spring to late fall, and the length of time to flowering can vary from 4 months to 22 months. A single taproot is formed.
Reproduction is by seed.
Seeds mature and may disperse within 7 to 10 days of flowering. Wind dispersal allows for movement over long distances. Seeds can remain viable in the soil for over 10 years. Each plant is capable of producing up to 10,000 seeds, which are dispersed by wind. These thistles typically do not pose a great threat to high quality natural areas, although they have been known to invade native and restored grasslands despite the presence of dense, native prairie vegetation.