Tanoak (Notholithocarpus densiflorus) is an evergreen tree in the beech family (Fagaceae), which includes beeches, oaks, and chestnuts. Despite producing acorns, it is not a true oak. It was formerly classified as Lithocarpus, and some sources may still use that name. Native to the western United States, tanoak grows from southwest Oregon to California, as far south as the Transverse Ranges.

Tanoak is slow-growing but remains a moderate size in garden settings. Unfortunately, it is highly susceptible to sudden oak death (Phytophthora ramorum), which has caused significant mortality within its range.

This tree provides critical habitat for wildlife. Its dense foliage offers cover for resting, hiding, and nesting, while its acorns are an important food source for birds such as Steller’s jay, band-tailed pigeon, varied thrush, and acorn woodpecker.

There are two recognized varieties of tanoak:

• N. densiflorus var. densiflorus – the more common variety
• N. densiflorus var. echinoides – a shrubbier form found in the northern part of its range.