Germination of Japanese Stewartia Seeds: The Effects of Warm and Cold Stratification

Abstract

Abstract Japanese Stewartia (Stewartia pseudocamellia (Maxim.)) is a species with outstanding landscape qualities, but is not widely available because reliable propagation protocols have not been developed, including procedures for overcoming seed dormancy. Three experiments were conducted to determine the warm and cold stratification requirements of Japanese Stewartia seeds. In the first experiment, seeds given a 3-day aerated water soak in 1 mM GA3, followed by 3 months warm moist stratification at 25C (77F) had greater germination 173 to 297 days after initiation of cold (7C, 45F) stratification than seeds given a 3-day aerated water soak and similar warm and cold stratification treatments. Final germination was 70%, but germination was not synchronous, it occurred over 172 days. In the second experiment, germination was low (less than 1%) for seeds given either 9 months cold moist stratification or 3 months warm moist stratification at 20C (68F) before 6 months cold moist stratification. Seeds given a 3-month warm moist stratification at an alternating 12 hr 20/12C (68/54F) cycles and 10 months cold moist stratification germinated from 30 to 93%, depending on mother tree. Germination was asynchronous, beginning after 150 days cold stratification and continuing for the next 165 days. In the third experiment, germination was not enhanced by a 3-day aerated water soak in either 1 mM GA3 or water, compared with seeds given no aerated water soak prior to cold moist stratification. Germination was greatest, 35%, for seeds given a 3-month warm moist stratification at 15C (59F) followed by at least 4 months cold moist stratification. However, germination was asynchronous. The results begin to identify the warm and cold stratification treatments that result in high germination.