Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2000
Publication Date: N/A
Interpretive Summary: Katsura trees, native to China and Japan, are not commonly cultivated in the United States. But these attractive landscape plants have few diseases or pests and seem to be well adapted to growing conditions found throughout much of the eastern United States and the Pacific Northwest. One of the factors limiting the use of katsura trees is that very little is known about their seed germination requirements. Experiments were conducted to help identify conditions that promote seed germination for the two known species of katsura. The best results were obtained by subjecting seeds to moist conditions at refrigerator temperature for eight days before allowing the seeds to germinate. This pre-chilling treatment sometimes caused the germination percentage to more than double, in the best case reaching an overall germination of 90 percent. Germinating untreated seeds under 15 hours of light was usually better than germinating them in darkness, but light had little or no effect on the pre-chilled seeds. Nursery growers can use the results of our experiments to improve the germination of katsura seeds, which should help make these beautiful trees more widely available.
Technical Abstract: Recommendations for seed propagation for katsura tree (Cercidiphyllum spp.) vary, and data that pertain to pretreatment and germination requirements of seeds are lacking in the literature. 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 +/- 0.5C (38.3 +/-.9F) for 8 days and germinating them at 25C (77F) in darkness or under a 15-hour photoperiod of 64 +/- 8 umol.m(-2).s(-1) photosynthetically active radiation for 21 days. Stratification was not required for germination, but did increase germination percentage, peak value, and germination value for both species. Stratification increased germination percentages of C. japonicum accessions 1150-67 and 882 from 41 percent to 90 percent and from 43 percent to 60 percent, respectively, and germination percentage of C. magnificum from 12 percent to 24 percent. Light enhanced germination percentages of unstratified seeds of C. japonicum accession 882 and of C. magnificum from 34 percent to 52 percent and from 8 percent to 15 percent, respectively. Stratification improved germinability of both species and obviated any preexisting light requirements the seeds may have had. We recommend that katsura seeds be stratified for at least 8 days, after which they can be germinated with or without light.