Notholithocarpus densiflorus, commonly known as the tanoak or tanbark-oak, is a broadleaf tree in the family Fagaceae, and the type species of the genus Notholithocarpus. It is native to the far western United States, particularly Oregon and California. It ranges from 15- in height, with a trunk diameter of 60-.
It can reach 40abbr=offNaNabbr=off tall in the California Coast Ranges, though 15- is more usual, and can have a trunk diameter of 60-. The bark is fissured, and ranges from gray to brown.
The leaves are alternate, 8-, with toothed margins and a hard, leathery texture. At first they are covered in dense orange-brown scurfy hairs on both sides, which wear off over time, more slowly on the underside of the leaf. The leaves will persist for three to four years.
The seed is an acorn 2- long and 2 cm in diameter, very similar to an oak acorn, but with a very hard, woody nut shell more like a hazel nut. The nut sits in a cup during its 18-month maturation; the outside surface of the cup is rough with short spines. The nuts are produced in clusters of a few together on a single stem.
Currently, the largest known tanoak specimen is on private timberland near the town of Ophir, Oregon. It has a circumference of 26order=flipNaNorder=flip, is about 2.51m (08.23feet) in diameter at breast height, and is 121abbr=onNaNabbr=on tall with an average crown spread of 56abbr=onNaNabbr=on.[1]
Members of populations in interior California (in the northern Sierra Nevada) and the Klamath Mountains in southwest Oregon are smaller, rarely exceeding 3m (10feet) in height and often shrubby, with smaller leaves, 4- long; these are separated as "dwarf tanoak", Notholithocarpus densiflorus var. echinoides. The variety intergrades with the type in northwest California and southwest Oregon. Tanoak grows as a shrub on serpentine soils.
By 2008, the species was moved into a new genus, Notholithocarpus (from Lithocarpus), based on multiple lines of evidence.[2] It is most closely related to the north temperate oaks (Quercus) and not as closely related to the Asian tropical stone oaks (Lithocarpus, where it was previously placed), but instead is an example of convergent morphological evolution.
While related to oaks (as well as chestnuts), the name is written as 'tanoak' because it is not a true oak.[3]
It is native to the far western United States, found in southwest Oregon and in California as far south as the Transverse Ranges and east in the Sierra Nevada. It grows from sea level to elevations of 1200m (3,900feet).
Tanoak is shade tolerant and benefits from disturbances. It is susceptible to wildfire and wounds that are exploited by rot fungi. It is one of the species most seriously affected by the disease "sudden oak death" (Phytophthora ramorum), with high mortality reported over much of the species' range.[4]
Fine hairs on the young leaves and twigs discourage deer from eating them. Various animals, including squirrels, deer, and bears, eat the nuts.
The nut kernel is very bitter, and is inedible for people without leaching. Some California Native Americans prefer this nut to those of many oak acorns because it stores well due to the comparatively high tannin content. The Concow tribe call the nut hä’-hä (Konkow language).[5] The Hupa people use the acorns to make meal, from which they would make mush, bread, biscuits, pancakes, and cakes. They also roast the acorns and eat them.[6] Roasted, the seeds can be used as a coffee substitute.[7] Samuel Thayer reports that despite their bitterness they are easy to dry, grind, and leach and produce a better-tasting flour than do acorns of oaks in the Quercus genus that he has processed.[8]
The name tanoak refers to its tannin-rich bark, a type of tanbark, used in the past for tanning leather before the use of modern synthetic tannins. By 1907, the use of tanoak for tannin was subsiding due to the scarcity of large tanoak trees. There were not enough trees around for a worthwhile economic return. By the early 1960s, there were only a few natural tannin operations left in California. The industry was beginning to switch to a synthetic alternative.[9] The tree's tannins has been used as an astringent.
A mulch made from the leaves of the tanoak can repel grubs and slugs.
The wood is strong and sometimes used as lumber, but suitable trees are usually inaccessible. It is also used as firewood.