Experimental evidence and evidence obtained from herbarium material suggest a pronounced difference in the biology of Senecio vulgaris L. var. vulgaris and ssp. denticulatus (O. F. Muell.) P. D. Sell. Whilst var. vulgaris is a plant of ruderal habitats, which can complete its life cycle in a very short time and can be found flowering all year round, ssp. denticulatus is a winter annual with an Atlantic–Mediterranean–montane distribution, which is strictly coastal outside the Mediterranean. It shows strong seed dormancy, which seems to be regulated by one major gene, and requires substantially more time to complete its life cycle than var. vulgaris. There is also some evidence that the reproductive potential of ssp. denticulatus is smaller than that of var. vulgaris. It seems likely that the ruderal var. vulgaris evolved from forms similar to ssp. denticulatus.