Time from seed dispersal to germination and time from germination to flowering are two key life history traits that determine fitness and coexistence of weeds in arable fields. Toorop et al. characterize these two traits in genotypes of Capsella bursa-pastoris (shepherd’s purse) and show an association between early flowering time and weak secondary dormancy. Three functional groups of seed dormancy are identified, varying in dormancy depth and nitrate response. One of these groups (FG-III) is distinct for early-flowering genotypes, conferring a selective advantage in arable fields.