Zigadenus densus and Z. leimanthoides are primarily southeastern Coastal Plain species, and both are rare in some parts of their range. Seeds have linear, underdeveloped embryos that are physiologically dormant; thus, they have morphophysiological dormancy. Cold stratification was the only requirement for embryo growth and dormancy break. Embryos in seeds of Z. leimanthoides grew from 0.43 to 2.47 mm in length during 9 weeks of cold stratification at 5°C. Nondormant seeds have a low temperature requirement for germination, and seeds that stayed at 5°C for 12 weeks began to germinate. In a nontemperature-controlled greenhouse, the first germination of seeds sown on 7 July was recorded on 28 December, at which time they had been exposed to 1,048 hours of cold stratifying temperatures (0-10°C). Germination in the greenhouse peaked between 2 January and 6 February, when mean daily maximum and minimum air temperatures were 10.9 and 3.0°C, respectively. In the field, dormancy break occurs during winter, and germination in late winter or early spring. No seeds germinated during the second germination season in the greenhouse, indicating that the species do not have the potential to form persistent seed banks.