Heuchera parviflora Bartl. var. parviflora occurs primarily in southeastern North America and H. cylindrica Dougl. var. cylindrica in northwestern North America. Both species are herbaceous perennials that grow in rocky habitats. Seeds of H. parviflora, collected in eastern Kentucky in November 1995 and 1996, and those of H. cylindrica, collected in western Washington in August 1996, were used to test temperature and light requirements for dormancy-break and germination and to determine germination phenology. Fresh seeds of H. parviflora germinated to 2-64% during 2 wk of incubation in light at alternating temperature regimes of 15/6, 20/10, 25/15, 30/15, and 35/20oC, with highest germination at 25/15oC; none of them germinated in darkness. Dry storage under laboratory conditions for up to 52 wk was not effective in overcoming dormancy. However, seeds given a 12-wk cold stratification period at 5oC in light germinated to 76-96% in light over the range of thermoperiods but those given cold stratification in darkness germinated to only 0-1% in darkness. Peak germination of H. parviflora seeds sown in November 1996 in a nonheated greenhouse occurred in early March 1997, when mean weekly maximum and minimum temperatures were 14.8 and 8.7oC, respectively. On the other hand, fresh seeds of H. cylindrica germinated to 0-37% during 2 wk of incubation in light at 15/6-35/20oC, with highest germination at 15/6 and 20/10oC, and none germinated in darkness. Seeds continued germinating to 76% at 15/6-20/10oC during 4-12 wk of incubation in light. Neither dry storage for up to 52 wk nor cold stratification at 5oC for 9 wk was effective in overcoming dormancy. Peak germination of seeds sown in the greenhouse in September 1996 occurred in late October 1996, when mean weekly maximum and minimum temperatures were 20.7 and 11.9oC, respectively.

Key words: germination ecology, Heuchera, Saxifragaceae