In the two centuries since its introduction into North America, ailanthus has probably become differentiated into genetically different subpopulations based on seed traits. Seed characteristics of ailanthus have been identified as traits that differentiate varieties and geographical strains. Ailanthus with bright red samaras compared to the more common greenish yellow has been named Ailanthus altissima var. erythrocarpa (Carr.) Rehd. A study of 11 seed sources from California and Eastern States found that seed width and weight were correlated with latitude (6). Northern sources have wider, heavier seed than the more southern sources.
- Burns, Russell M., and Barbara H. Honkala, technical coordinators. 1990. Silvics of North America: 1. Conifers; 2. Hardwoods. Agriculture Handbook 654 (Supersedes Agriculture Handbook 271,Silvics of Forest Trees of the United States, 1965). U.S. Department of Agriculture, Forest Service, Washington, DC. vol.2, 877 pp. http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_of_contents.htm
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