Tanoaks develop deep taproots (22) and also develop intricate systems of lateral roots which may approach the soil surface and grow downhill, eventually emerging from the soil where they form burls that produce sprouts.
The sapwood of tanoak is extremely thick, reaching a high of 66 percent even on large trees. This condition helps trees to live after the bark has been stripped for tannin production or after trees have been girdled for eradication. Some girdled trees have lived as long as 30 years.
- 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