Tanoak Notholithocarpus densiflorus

Tanoak is not a true oak — it belongs to its own unique genus, Notholithocarpus. Found in southern Oregon and northern California, this evergreen hardwood is one of the most important mycorrhizal host trees in the southern part of our region. If you forage for chanterelles or boletes south of the Umpqua, you are almost certainly walking through tanoak habitat.

Tanoak produces tannin-rich acorns and has thick, leathery evergreen leaves with a fuzzy underside. The bark is furrowed and dark. It grows as both a tall canopy tree and a shrubby understory species, depending on conditions. In the Klamath-Siskiyou region, tanoak is a keystone species for fungal diversity.

For mushroom hunters working southern Oregon, tanoak is the tree to know. The mixed tanoak-Douglas fir forests of the southern Coast Range, Siskiyou Mountains, and Rogue Valley produce some of the best chanterelle and bolete harvests in the region. Tanoak’s mycorrhizal partnerships rival those of Douglas fir in these areas.

Tanoak faces a serious threat from sudden oak death (Phytophthora ramorum), which has devastated populations in northern California and is present in parts of Curry County, Oregon. The loss of tanoak from these forests would significantly reduce mushroom productivity. This makes tanoak forests worth understanding — and worth protecting.