Seed germination ecology of poison hemlock, Conium maculatum

Abstract

In north-central Kentucky, United States, seeds of Conium maculatum are dispersed from mid-September to mid to late February, with up to 95% of them being dispersed by late December. Depending on the year, 40–85% of the freshly matured seeds had morphological dormancy (MD) and thus needed only a moist substrate, 10–15 14-h photoperiod days and 12-h alternating thermoperiods of 30:15 °C for embryo growth and germination. The other seeds had morphophysiological dormancy (MPD), and embryo dormancy had to be broken before embryo growth and germination could occur. MPD was broken in some of the undispersed seeds during summer, and by September 50–85% (depending on the year) germinated at 25:15 °C in light. During late autumn and winter, 35–95% (depending on the year) of the undispersed seeds in MD in autumn entered MPD. Cold stratification at 5 °C induced about half the seeds with MD into MPD. Seeds in MD germinated to higher percentages on soil than on sand, and in light than in darkness. Most of the seeds sown on soil in a nonheated greenhouse in July, August, and September germinated in September. Seeds sown in October and November germinated in autumn, late winter, and the following autumn, and those sown in late winter germinated in spring and autumn. The later seeds were sown, the higher germination percentages were the following autumn. Key words: dispersal, dormancy, germination, morphological dormancy, poison hemlock, Conium maculatum, monocarpic perennial.