Quercus pacifica |
Quercus agrifolia |
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Channel Island scrub oak, island scrub oak, Pacific oak |
California live oak, coast live oak, encina |
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Habit | Shrubs, rarely small trees, subevergreen, shrubs to 2 m, trees to 5 m or taller. | Trees, evergreen, to 25 m. Bark gray to dark brown or black, ridges broad, rounded. |
Bark | scaly on older branches and trunk. |
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Twigs | brownish or reddish, minutely puberulent, becoming glabrate and gray with age. |
brown to red-brown, 1.5-3 mm diam., with scattered pubescence or uniformly pubescent. |
Buds | light or chestnut brown, ovate or globose, 2-3 × 1-2 mm. |
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Leaves | blade obovate or oblong, planar to moderately convex or undulate, 15-40 × 7-20(-40) mm, base cuneate or rounded, attenuate-decurrent along petiole, margins minutely cartilaginous, entire or with 1-5 irregular teeth on each side, secondary veins obscure, 1-5 on each side, apex blunt or rounded, occasionally subacute with mucronate tip; surfaces abaxially waxy, glandular, with scattered minute, flat, appressed, ± 8-rayed stellate hairs, not obscuring surface, adaxially green, glossy, glabrate or with minute, scattered, stellate hairs. |
blade broadly elliptic to ovate or oblong, 15-75 × 10-40 mm, base rounded or cordate, margins entire or spinose, with up to 24 awns, apex blunt to attenuate; surfaces abaxially glabrous or with small axillary tufts of tomentum, veins raised, adaxially distinctly convex, rugose, glabrous, occasionally densely uniformly pubescent. |
Acorns | paired or solitary in leaf axil, subsessile, rarely pedunculate in teratological forms; cup hemispheric to turbinate, to 15 mm deep × 20 mm wide, enclosing only 1/4-1/2 nut, scales moderately to heavily tuberculate, irregularly formed; nut light brown, acute-cylindric or fusiform, tapered, (15-)20-30 × (6-)9-15 m, apex acute, glabrate. |
annual; cup turbinate to cup- or bowl-shaped, rarely saucer-shaped, 9-13 mm high × 9-15 mm wide, covering 1/4-1/3(-1/2) nut, outer surface glabrous to sparsely puberulent, inner surface pubescent on innermost 1/3 to uniformly pubescent, scales acute, tips loose; nut ovoid to oblong or conic, 15-35 × 10-15 mm, glabrous, scar diam. 3.5-8 mm. |
Cotyledons | distinct. |
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Terminal | buds light chestnut brown, ovoid, occasionally subconic, 3-6(-7) mm, glabrous except for cilia along scale margins. |
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2n | = 24. |
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Quercus pacifica |
Quercus agrifolia |
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Phenology | Flowering spring. | Flowering early to mid spring. |
Habitat | Chaparral, oak woodlands, margins of grasslands, understory in closed-cone pine stands | Moderately dry sites |
Elevation | 0-300 m (0-1000 ft) | 0–1400 m (0–4600 ft) |
Distribution |
CA
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CA; Mexico (Baja California)
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Discussion | Of conservation concern. Quercus pacifica is endemic on three of the California Channel Islands: Santa Cruz, Santa Catalina, and Santa Rosa. It is not known from the mainland, but it bears a superficial similarity to some of the tree forms that are putative hybrids between Q. engelmannii and Q. cornelius-mulleri in San Diego County. The latter populations, sometimes treated as Q. ×acutidens, differ in having much greater variability in leaf shape; thicker, more leathery leaves; denser abaxial leaf vestiture; much smaller hairs, having more than 10 rays; and variable levels of connation of cotyledons (always distinct in Q. pacifica). Quercus pacifica appears to be most closely related to Q. douglasii, whether by direct descent or by introgression with another species no longer extant on the islands. Quercus ×macdonaldii Greene (as a species) [= Quercus dumosa var. macdonaldii (Greene) Jepson] is a stabilized hybrid complex between Quercus pacifica and Q. lobata Née. The plants tend to be small to moderate trees with leaves that resemble those of Q. lobata; the leaves are much more shallowly lobed and always less than two-thirds the distance from the margin to the midrib. Quercus ×macdonaldii is known from Santa Rosa, Santa Cruz, and Santa Catalina islands. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Quercus agrifolia is found in the Coast Ranges from Sonoma County, California, south to Baja California. Plants with densely pubescent leaves, especially abaxially, have been treated as Q. agrifolia var. oxyadenia. This species reportedly hybridizes with Quercus kelloggii and Q. wislizenii. The Mahuna used Quercus agrifolia medicinally to heal the bleeding navel of a newborn (D. E. Moerman 1986). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 3. | FNA vol. 3. |
Parent taxa | Fagaceae > Quercus > sect. Quercus | Fagaceae > Quercus > sect. Lobatae |
Sibling taxa | ||
Synonyms | Q. dumosa var. polycarpa | Q. acroglandis, Q. agrifolia var. oxyadenia, Q. pricei |
Name authority | Nixon & C. H. Muller: Novon 4: 391. (1994) | Nee.: Anales Ci. Nat. 3: 271. (1801) |
Web links |