Mark P. WidrlechnerU.S. Department of Agriculture-Agricultural Research Service, North Central Regional Plant Introduction Station, Iowa State University, Departments of Agronomy and Horticulture, Ames, IA 50011-1170.
Germinability of two, half-sib seed sources of Cercidiphyllum japonicum Sieb. & Zucc. and one seed source of Cercidiphyllum magnificum (Nakai) Nakai was determined after not stratifying or stratifying seeds at 3.5 ± 0.5 °C (38.3 ± 0.9 °F) for 8 days followed by germination for 21 days at 25 °C (77 °F) in darkness or under a 15-hour photoperiod. Stratification was not required for germination, but increased germination percentage, peak value, and germination value for both species. Stratification increased germination of C. japonicum from 42% to 75%, and germination of C. magnificum from 12% to 24%. Light enhanced germination of nonstratified seeds of one source of C. japonicum and of C. magnificum from 34% to 52% and from 8% to 15%, respectively. Stratification improved germinability of both species and obviated any preexisting light requirements the seeds may have had.