Blue Oak (Quercus douglasiiis a deciduous oak tree that is native to Davis. Highly drought tolerant, it invests much of its energy into root growth so as to find water in dry soil. It is therefore unusually slow growing above ground, increasing in height by no more than about a foot or so per year even under the best of conditions. It can live to be over 500 years old but never exceeds 100 feet in height.

Blue Oak is categorized as a white oak and is therefore immune to the sudden oak death pathogen. Its leaves have a bluish tint that helps reflect the heat of the sun rather than absorbing it; the leaves become bluer when the tree is more drought stressed. The leaves are usually 2–4 inches long and often have lobed edges. The acorns are usually about 1 inch long. The tree prefers full sun or partial shade.

Blue Oak takes its scientific name from David Douglas.