A white oak type, Bur Oak is very drought tolerant. A deep cap, conspicuously fringed at the margin, encloses 1/2 or more of the acorn. This tree is very adaptable to clay and alkaline soils. Its acorns are the largest of all native oaks, up to 1.5 inches long, and are important wildlife food. Leaf sinuses,indentations between lobes, sometimes extend almost to the midrib, and lobes are rounded and irregular. Branches develop distinctive corky ridges after the first year.