Hybrids between black spruce and red spruce are common, and introgressive hybridization between the two species has been reported in Nova Scotia, New Brunswick, and Quebec (14,32).
A natural hybrid between black spruce and white spruce found in northern Minnesota has been called the Rosendahl spruce (28). Intermediate forms between black and white spruce have been reported occasionally from other areas (41), but the genetic isolation of these two species must be nearly complete.
- 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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