Flora of the Pacific Northwest, Hitchcock and Cronquist, University of Washington Press, 7th printing, 1973.
Seeds of the Woody Plants in North America, Young and Young, Dioscorides Press, 1992.
Seeds of the Woody Plants in the United States, Agriculture Handbook No. 450, U.S.F.S., Washington D.C., 1974.
Seed Germination Theory and Practice, 2nd Edition, Deno, N., published June,1993.
Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination, Baskin and Baskin, Academic Press, 1998.
Propagation of Pacific Northwest Native Plants, Rose,R., Chachluski, C., and Haase, D. Oregon State University Press, 1998.