Seeds of the southeastern North American Schoenolirion croceum (Michx.) Wood are dispersed in late spring/early summer in middle Tennessee. If fresh seeds are buried in soil following dispersal, they germinate in autumn. However, fresh seeds sown on the soil surface following dispersal germinate the following late winter/early spring. To determine the cause(s) for this difference in germination phenology, we examined the temperature and light requirements for dormancy break and germination. Freshly matured seeds did not germinate during 2 weeks of incubation at any of the alternating thermoperiods of 15/6, 20/10, 25/15, 30/15, and 35/20oC in light or darkness. No seeds germinated during 2 weeks of incubation at 15/6-35/20oC in light following 12 weeks of warm stratification at 25/15oC in light, whereas 80-95% germinated in darkness following warm stratification in darkness. On the other hand, seeds germinated to 1-69% in light and 17-93% in darkness during 2 weeks of incubation at 15/6-35/20oC following 12 weeks of cold stratification at 5oC in light and darkness, respectively. If seeds were exposed to light during simulated summer (30/15-35/20oC), autumn (15/6-20/10oC), and winter/early spring (5oC) temperatures, they germinated to high percentages in winter/early spring. Seeds exposed to light during summer and darkness during autumn and those exposed to darkness during both summer and autumn germinated to high percentages in autumn. However, seeds exposed to darkness during summer and light during both autumn and winter/early spring germinated to high percentages in winter/early spring. Thus, light conditions during autumn are critical for determining whether seeds will germinate in autumn or winter/early spring. In contrast to many other species in which germination phenology is mostly controlled by temperature, the timing of germination for S. croceum depends on the light conditions in relation to temperatures experienced during dormancy release.

Key words: Hyacinthaceae, light requirements, Liliaceae, Schoenolirion croceum, seed dormancy, seed germination