island scrub oak

Quercus pacifica is a shrub or a small tree growing up to 5 meters (16 feet) in height, or occasionally taller. The leaves are roughly oval in shape and have entire, wavy, or toothed edges. The green blades are up to 4 centimeters (1+1⁄2 inches) long by 4 cm wide. They have shiny upper surfaces and waxy, hairy, glandular undersides. The acorn has a cap up to 2 cm (3⁄4 in) wide and a nut measuring 2 or 3 cm (3⁄4 or 1+1⁄4 in) long.

This oak often produces a stable hybrid with Quercus lobata, that has been named Quercus × macdonaldii.

It is endemic to the Channel Islands of California, where it is known from the islands of Santa Cruz, Santa Rosa, and Santa Catalina. The islands of Santa Cruz and Santa Rosa are part of Channel Islands National Park. Though limited to three islands, it is not uncommon there, occurring in grassland, chaparral, oak woodlands, forest, and other habitat. It is the dominant oak in many areas on Catalina Island. It was described as a new species in 1994 from a specimen collected on Santa Cruz Island. More than a century earlier, the same plant was described as a variety of Quercus dumosa; the 1994 name is nevertheless the correct name for the plant when recognized as a species because names hold priority status only within a given rank.