California black oak (Quercus kelloggii). Illustration by Jeanne R. Janish from Hitchcock et al. 1969, Vascular Plants of the Pacific Northwest, courtesy of University  of Washington Press.

     (Editor’s note:  Part I of Dr. Chambers’ article on the family Fagaceae appeared in the October, 1998 issue of OFN.)

     The genus Quercus in Oregon is represented by five species, plus one named and several unnamed hybrids.  If we divide them into three groups, White Oaks, Red or Black Oaks, and Golden-cup Oaks, we can note similarities and differences among certain of the taxa. Following are the major features of each group and the species that occur in Oregon.

     White Oaks - Leaves deciduous (ours), lobed but without awned teeth; acorns take one year to mature; cup scales may be tomentose but not embedded in the pubescence [species in Oregon: Quercus garryana].

     Red or Black Oaks - Leaf blades, if lobed, then with awned teeth (if entire, then often with a bristle at the leaf apex);  acorns generally take two years to mature; cup scales are not embedded in  tomentum  [Q. kelloggii and Q. sadleriana].

     Golden-cup Oaks - Evergreen with leathery, entire or awn-toothed
leaves; acorns take two years to mature; cup scales are embedded  in tawny or glandular tomentum [Q. chrysolepis and Q. vaccinifolia].

     Many oak hybrids have been reported and named, particularly within the White and Red/Black groups.  In most cases, hybridization results in solitary trees or small groups of intermediate individuals.  Occasionally hybrid populations occur which cover a large geographic range.

     Our single White Oak species, Q. garryana Douglas ex Hook var. garryana (Garry oak) is the most conspicuous and widespread of  Oregon’s oaks.  These trees occur at low elevations from British Columbia to California.  A shrubby or small tree variant, var. breweri, once considered a separate species, occurs at 1400-1900 m in elevation in the Siskiyou region of northern California and southern Oregon.  Very few of the herbarium specimens of this taxon designate the size of the tree that the twig has come from, but the buds of var. breweri are generally small, rounded and reddish, while those of var. garryana are more elongate and yellowish to cream in color.

     Quercus kelloggii Newb. (California black oak) is widespread in California and occurs in Oregon as far north as Lane County.  The trees are up to 25 m in height with deciduous leaves that are lobed and have teeth with bristles.  The distinctive acorns have a cap that covers approximately three-fourths of the nut, and the scales are broad and up to 4 mm in length.

     [Do Quercus garryana and C. kelloggii hybridize where they come in contact in southern Oregon?  Anecdotal evidence from the Eugene area suggests that they may, but as far as we know, the hypothesis has not been tested.  Editor]

     Quercus sadleriana R. Br. (Sadler’s oak) is endemic to a small area that spans the Oregon-California border in the Siskiyou Mountains.  This shrub species is one of the most distinctive western oaks.  The large (up to 14 cm long), evergreen leaves are obovate to elliptic and have prominent veins and coarsely serrate margins.

     Quercus x morehus Kellogg (oracle oak) is a hybrid between Q. kelloggii and Q. wislizeni A. DC (Sierra live oak, interior live oak), a widespread California species that includes trees and shrubs.  The hybrids are known from several populations that occur from northern Douglas County to southern Josephine County as well as California.  The entire to spinose margins of Q. wislizeni are apparent in the leaves of the hybrid, which are quite intermediate between the two parents.

     Quercus chrysolepis Liebm. (canyon live oak, maul oak) is a widespread and variable species that occurs on ridges, canyons and rocky slopes from 200-2600 m in elevation.  These plants range from medium-sized trees to shrubs.  The evergreen leaves can be oblong or acuminate, and the margins vary from entire to spinulose-dentate.  Both leaf forms may occur on the same plant. The lower leaf surface has a dense layer of golden, glandular and multiradiate hairs, especially early in the season.  The acorn cap varies from saucer-shaped to turbinate; the acorns are oblong to fusiform.  This species grows from Mexico to southern Oregon and east to New Mexico and Nevada.  Its great diversity led earlier workers to name several varieties, but more recent study does not support the recognition of subspecific taxa.

     Quercus vaccinifolia Kellogg (huckleberry oak) is a shrubby evergreen species that grows on dry ridges and rocky slopes from 900 to 2800 m from northwestern Nevada to northern California and  southern Oregon (Josephine and Curry Counties).  These low shrubs are prostrate or erect and up to 1.5 m tall.  Their leaves resemble those of huckleberry but have a more leathery texture.  The leaves may be entire or have irregular, mucronate teeth.  This taxon can be distinquished from Q. chrysolepis by the absence of glandular trichomes on the undersides of the leaves, which are glaucous below, and by thinner acorn cups and smaller nut-attachment scars.  These two species of golden-cup oaks hybridize at lower elevations in northern California and southern Oregon.