Members of populations in interior California (in the northern Sierra Nevada) and the Klamath Mountains into southwest Oregon are smaller, rarely exceeding 3 m (9.8 ft) in height and often shrubby, with smaller leaves, 4–7 cm (1.6–2.8 in) long; these are separated as "dwarf tanoak", Notholithocarpus densiflorus var.
echinoides.
The variety intergrades with the type in northwest California and southwest Oregon.
Tanoak does grow on serpentine soils as a shrub.
Members of populations in interior California (in the northern Sierra Nevada) and the Klamath Mountains into southwest Oregon are smaller, rarely exceeding 3 m (9.8 ft) in height and often shrubby, with smaller leaves, 4–7 cm (1.6–2.8 in) long; these are separated as "dwarf tanoak", Notholithocarpus densiflorus var. echinoides. The variety intergrades with the type in northwest California and southwest Oregon. Tanoak does grow on serpentine soils as a shrub.
Notholithocarpus