roots are shallow spreading, often apparent at the soil surface, and roots near the trunk thicken into enlarged storage structures. These large rounded structures are assumed to be for water storage, contributing to the drought hardiness of the species (4). There is a general absence of a taproot with most roots present in the upper 46 cm (18 in) of soil. Within this zone, the deeper roots send numerous small roots to the surface. Adventitious shoots may arise from any of the surface roots.
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.