[6][7] Quercus douglasii is a medium-sized tree with sparse foliage, generally 6–20 meters (20–66 feet) tall, with a trunk 36–60 centimeters (1–2 ft) in diameter at breast height.

[10] Its sparse foliage allows more light to reach the ground, and young trees may grow for decades below their parents' canopies.

[15] Natural hybrids between Q. douglasii and the related Q. lobata, Q. garryana,[5] and shrub live oak (Q. turbinella) often occur where the species grow together in the same area.

It has a smaller canopy than less drought-tolerant relatives, and invests proportionally more growth into roots rather than leaves throughout its life cycle.

[5] Author Ron Russo writes that Q. douglasii hosts the "largest number of known species" of gall wasps,[19] at more than 50.

[20] The wasps trigger the formation of oak galls in a wide variety of shapes, colors, and sizes.

They made baskets out of blue oak seedlings, utensils such as bowls from the wood, and dye from the acorns.