Park visitors should have no difficulty recognizing this tree. It is not only one of the most distinctive and beautiful trees in the park, but in its resemblance to the eastern black oak it possesses many of the characters typical of the oak group with which most people are familiar. It grows on benches and valley bottoms in dry, gravelly to sandy soils, from 3,000 to 5,000 feet above sea level. It is one of the most common trees on the floor of Yosemite Valley where it forms picturesque groves of great charm and beauty. Here in autumn the rich color of its foliage, which ranges from tawny yellow to rich golden brown, is a highlight of that season. Upon unfolding in the spring the leaves are pink and velvety, soon changing to a glossy green as they develop to about four or five inches in length with the advent of summer. The under side of the leaves is a lighter green than the upper surface. They are borne alternate on the branches, are thin and deeply cleft into about seven lobes, each with one to four bristle-tipped teeth.

The trunk is generally short and massive and free of limbs for only about ten to twenty feet above the ground. Large, heavy limbs branching from the trunk form a broad, spreading, open, rounded crown. The bark on old trunks and the base of

Foliage and acorns of black oak (Inch squares on background)

[click to enlarge]

Photo by Brockman

Foliage and acorns of black oak (Inch squares on background)

large limbs is dark gray to black in color, hard, rough, and deeply furrowed. Small trees and the outer portions of larger limbs are characterized by bark that is smooth and of a dull gray-brown color. Year old twigs are smooth and red to reddish-brown. The buds are alternate on the twigs; and, in addition, are clustered at the tips, are ovoid to conical in shape and covered with numerous five-ranked scales. The leaf scars, moderate to small in size, are half round in outline and characterized by nearly a dozen vascular bundle scars arranged more or less in the form of an ellipse.

One of the most distinctive features of the California black oak are the acorns. These mature at the end of the second season and are produced in abundance at intervals of from two to three years. They are one to one and one-half inches long, a pale chestnut in color, and are possessed of a tawny brown, scaly cup.

Acorns of this tree served as the principal source of food for the Indians of the area in the early days. They were pounded into coarse flour by the Indian women. Numerous mortar rocks, scattered about the Valley, are reminiscent of the original residents of this area since they are characterized by depressions brought about by that task. California black oak acorns are still gathered and utilized as food to some extent by a few of the older Indian residents of the Yosemite region.

[click to enlarge]
Photo by Ansel Adams

All oaks are wind pollinated. Thus these trees are rendered conspicuous in the early spring when, at about the time the leaves are beginning to develop, they are festooned with numerous loose, pendent, tassel-like staminate catkins which bear the abundant pollen.

Mature specimens of the California black oak are from 75 to 80 feet tall and one and one half to three feet in diameter. It is a moderately long-lived tree, attaining an age of about 300 years. Large trunks of old trees, however, are rarely sound. These are generally characterized by decayed centers and are often broken at the top. Such specimens often furnish nesting sites for California woodpeckers and occasionally one will find a dead tree whose trunk and larger branches serves as a “storage bin” for these birds. In such instances these trunks are studded with holes in which acorns have been tightly wedged.

Another feature of interest relative to the California black oak is the abundance of mistletoe (Phoradendron villosum) found in these trees. This, a parasitic plant, appears as loose, bushy clusters, one to three feet in diameter, among the branches. It is particularly noticeable during the winter when the tree is barren of foliage.

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