Some seed is viable 8 days after flower initiation. Most seed does not appear to require an afterripening period. Seed germination is closely correlated with rainfall events. Large flushes of seed germinate after the first fall rains, but smaller germination flushes can occur nearly year round. Non-pappus bearing seeds appear to require higher temperatures to germinate than pappus bearing seeds.
Light is required for seed germination.
Seed can survive for up to 10 years in the field, depending on environmental conditions, but it appears that few seeds survive beyond 2-3 years in the Central Valley. Shaded conditions reduce flower production and root growth. In some areas, flowering plants may be found year-round in areas not exposed to severe frost. Yellow starthistle litter appears to inhibit germination of its seeds, probably by blocking light penetration. Young seedlings are especially resistant to the effects of fall drought.