Coast live oak

Appearance

Coast live oak typically has a much-branched trunk and reaches a mature height of 10–25 metres. Some specimens may attain an age exceeding 1,000 years. Examples of this include the Grand Oak of Cherry Valley, California, the Encino Oak Tree, which died in the 1990s and the Pechanga Great Oak.

The trunk, particularly for older individuals, may be highly contorted, massive and gnarled. The crown is broadly rounded and dense, especially when aged 20 to 70 years; in later life the trunk and branches are more well defined and the leaf density lower. The oldest specimens might exceed 6 m in trunk circumference and 30 m in height.

The leaves are dark green, oval, often convex in shape, 2–7 centimetres long and 1–4 cm broad; the leaf margin is spiny-toothed, with sharp thistly fibers that extend from the lateral leaf veins. The outer layers of leaves are designed for maximum solar absorption, containing two to three layers of photosynthetic cells.

These outer leaves are deemed to be small in size to more efficiently re-radiate the heat gained from solar capture. Shaded leaves are generally broader and thinner, having only a single layer of photosynthetic cells. The convex leaf shape may be useful for interior leaves which depend on capturing reflected light scattered in random directions from the outer canopy.

The flowers are produced in early-to-mid spring; the male flowers are pendulous catkins 5–10 cm long, the female flowers inconspicuous, less than 0.5 cm long, with 1–3 clustered together. The fruit is a slender reddish brown acorn 2–3.5 cm long and 1–1.5 cm broad, with the basal quarter enclosed in a cupule; unusually for a red oak, the acorns mature about 7–8 months after pollination.

File:cloe06.jpg|Coast live oak, Sonoma County
File:cloacorne.jpg|Acorns and leaves

Naming

In naming the species, Née compared it to a species illustrated in Leonard Plukenet's "Phytographia" under the descriptive name ""Ilex folio agrifolii americana, forte agria, vel aquifolia glandifera"" which Plukenet had compared, in his "Almagestum botanicum", to Luigi Anguillara's "Agrifolia glandifera", the noun Agrifolia being a Medieval Latin form of Aquifolium meaning a holly or holly-leaved oak, and related to the Modern Italian Agrifoglio",' meaning 'holly.'

Habitat

Normally the tree is found on well-drained soils of coastal hills and plains, often near year-round or perennial streams. It may be found in several natural communities including coast live oak woodland, Engelmann oak woodland, valley oak woodland and both northern and southern mixed evergreen forests. While normally found within 100 kilometers of the Pacific Ocean at elevations less than 700 m, in southern California it occasionally occurs at up to 1,500 m in altitude.

It is the only California native oak that thrives in the coastal environment, although it is rare on the immediate shore; it enjoys the mild winter and summer climate afforded by ocean proximity, and it is somewhat tolerant of aerosol-borne sea salt. The coastal fog supplies relief from the rainless California summer heat.

It is the dominant overstory plant of the coast live oak woodland habitat, often joined by California bay laurel and California buckeye north of Big Sur. Associated understory plants include toyon, various manzanitas and western poison-oak.The California oak moth caterpillar subsists entirely on living and fallen leaves of the Coast Live Oak. In 8–10 year cycles, the caterpillar will appear in sufficient abundance to denude healthy trees. The trees recover, and botanists speculate that the species provide mutual benefit, possibly in the form of fertilizer for the oak. The coast live oak is also the only known foodplant of "Chionodes vanduzeei" caterpillars.