What Is a Tanoak?

A tanoak, also called a Tanbark-oak, is an evergreen shrub or tree primarily found in Oregon and along California's Pacific coasts, as well as in Malaysia and other parts of southeast Asia. It often grows in areas in or above mixed evergreen forests. These habitats may be located at sea level or higher elevations with steep, rough terrain and well-drained soil. Tanoak is a beneficial plant to local wildlife as a habitat and food source, and it is harvested for a variety of uses.

The plant is a member of the beech, or Fagacceae, family. Historically, it was given the scientific name Lithocarpus densiflorus, but research published in 2008 suggests it belongs in a new genus, Notholithocarpus densiflorus. This hardwood evergreen is similar to oak and chestnut and may grow as a shrub or tree.

Common height ranges from 65 to 80 feet (20 to 24 m), though dwarf varieties may reach only 10 feet (3 m) tall. Its long, straight trunks grow between 0.5 to 2.5 feet (0.2 to 0.8 m) in diameter, and branches spread outward and up, where evergreen catkin leaves, blossoms, and acorns grow from. These trees can live from 80 to 300 years.

These trees are distributed between southern Oregon, California, and southeast Asia. They are typically located in mixed-evergreen and redwood forests, especially along the Pacific coast. Tanoak is also sometimes found in areas above those habitats. The Douglas fir is commonly found living alongside the tanoak, among other types of conifers.

Tanoak is largely found in humid climates, though precipitation amount and type varies. Average daily temperatures in these environments range from 36° to 74° Fahrenheit (about 2° to 23° Celsius). The plant can be found in elevations from sea level up to 5,000 feet (1,524 m) high where terrain is typically very steep and ragged. It grows well in deep soil with a sandy, loamy, or gravel texture and good drainage. This tree cannot typically thrive in heavy, clay earth.

The tree's acorns serve as a food source for local wildlife, including birds, deer, and rodents, among others. It also provides nesting areas and warm cover for several small animals. Tanoak injured by fire is susceptible to fungal infection, specifically white root rot and weeping conk, though other diseases are common.

Common uses of tanoak include as lumber for a variety of hardwood products including furniture, flooring, and firewood. It has a high concentration of tannin extracted for use in leather, a practice which peaked at the beginning of the 20th century. The acorns were once a staple food of local Native American tribes as well.