Quercus agrifolia

''Quercus agrifolia'', the California live oak, or coast live oak, is an evergreen live oak native to the California Floristic Province. Live oaks are so-called because they keep living leaves on the tree all year, adding young leaves and shedding dead leaves simultaneously rather than dropping dead leaves en masse in the autumn like a true deciduous tree. Coast live oaks may be shrubby, depending on age and growing location, but is generally a medium-sized tree. It grows west of the Sierra Nevada mountain range from Mendocino County, California, south to northern Baja California in Mexico. It is classified in the red oak section of oaks (''Quercus'' sect. ''Lobatae''), subsection ''Agrifoliae''.

This species is commonly sympatric with canyon live oak (''Q. chrysolepis''), and the two may be hard to distinguish because their spinose leaves are superficially similar.

Description

Coast live oak typically has a much-branched trunk and reaches a mature height of . 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 (part of the stump has been preserved) and the Pechanga Great Oak. The tree is extremely drought-toleran


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 in trunk circumference and in height.

The leaves are dark green, oval, often convex in shape, long and broad; the leaf margin is spiny-toothed (spinose), 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 leaf shape may be also useful as condensation surfaces for "dew and mist, which would allow the tree to survive years with limited rainfall".

The flowers are produced in early-to-mid spring; the male flowers are pendulous catkins long, the female flowers inconspicuous, less than long, with 1–3 clustered together. The fruit is a slender reddish brown acorn long and broad, with the basal quarter enclosed in a cupule; unusually for a red oak, the acorns mature about 7–8 months after pollination (most red oak acorns take 18 months to mature).

Recognized varieties

There are two varieties of ''Quercus agrifolia'':

Hybridity

Several hybrids between coast live oak and other red oak species have been documented. Hybrids with interior live oak (''Q. wislizenii'') are known in many areas in northern California. Coast live oak also hybridizes with Shreve oak (''Q. parvula'' var. ''shrevei''). All these oak species show evidence of introgression with one another.

Etymology

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'.

Distribution and habitat

The Coast Live Oak is typically found within 100 km (62 mi) of the Pacific Ocean, living on coastal hills and plains and preferring soil with good drainage as well as proximity to perennial streams. It often lives in communities with other native oaks and sometimes in mixed evergreen forests. It generally prefers elevations less than , but can be found as high as in some places. The Coast Live Oak typically enjoys the climate of near-coastal environments; it has a higher-than-average tolerance for airborne salinity, allowing coastal fog to make up for the lack of rain during much of the year.

Ecology

Coast Live Oaks are the dominant tree in the Coast Live Oak Woodland habitat. This habitat often contains other shrubs and vines, including toyon, California coffeeberry, California man-root, bitter gooseberry, California wild rose, Hummingbird sage, blue elderberry, and poison-oak.

The caterpillars of the California oak moth ('' Phryganidia californica'') subsist entirely on living and fallen leaves of the Coast Live Oak. In 8–10 year cycles, the caterpillars 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.

Live oak trees, among other western oaks, are also known to support acorn woodpeckers, which store their acorns in tree trunks and remove them when they want to eat.

Allergenicity

The pollen of the coast live oak is a severe allergen. Pollination occurs in spring.

Uses

Historical

At least twelve distinct cultures of Native Americans are known to have consumed the acorns as a dietary staple. The seeds were ground into meal, which after being washed was boiled into mush or baked in ashes to make bread. A particular usefulness of the tree lies in its ability to yield acorns in winter season as we

In the 18th century, Spanish colonization of the Americas, Spaniards in the San Fernando Valley used the wood for charcoal to fire kilns in making adobe. Later this form of charcoal would be utilized in the baking, gunpowder and electric power industries.

In the 18th and 19th centuries shipbuilders sought out the odd angular branches to make special joints. Pioneers moving west would harvest small amounts for making farm implements and wagon wheels, but the greatest impact was the wholesale clearing of oak woodlands to erect sprawling cities such as San Diego and San Francisco. The irregular shape often let the tree escape widespread harvest for building timbers, and also led the early settlers to endow the coast live oak with mystical qualities. Its stateliness has made it a subject of historical landscape painters throughout California modern history since the mid-19th century.

Modern

Coast live oak has also become a common addition to western US landscaping. It is however sensitive to changes in grading and drainage; in particular, it is important to respect the root crown level and avoid adding soil near the trunk when construction or landscaping occurs.

Also, if incorporating it into a landscaping scheme with artificial irrigation, it is important to avoid regular watering within the oak's drip line (canopy), since wet soil in the summer increases infection rates by soil-borne ''Phytophthora'' diseases like sudden oak death.

Santa Maria–style barbecue is grilled over coals of coast live oak.

Culture

The coast live oak, especially in its Spanish forms ''encino'' or ''encina'', ''encinitas'' "little oaks", and ''encinal'' "oak grove", gave its name to seven land grants across California and to many communities and geographic features. These include Rancho Los Encinos, the Los Angeles community of Encino, Encinitas near San Diego, and Encinal del Temescal, now the city of Oakland.Gudde, Erwin, and William Bright, ''California Place Names'', University of California Press, 4th edition, 1998, , pp. 123–124

Paso Robles (fully 'El Paso de Robles' or 'Pass of the Oaks') also refers to the ubiquitous live oaks in the region as a geographical place name.

References

Bibliography

*
* C. Michael Hogan, California Arts and Sciences Institute calasinstitute.org (2023) ''Coast Live Oak''. ed. Arthur Dawson. Encyclopedia of Earth. National Council for Science and Environment. Washington DC
*
*
*
*

External links

*

Las Pilitas: California Oaks

Virginia Tech Forestry Department: Coast Live Oak

USDA Plants Database: ''Quercus agrifolia'' Née

Interactive Distribution Map for ''Quercus agrifolia''

{{Authority control

agrifolia
Flora of California
Trees of Northern America
Natural history of the California chaparral and woodlands
Natural history of the California Coast Ranges
Natural history of the Central Valley (California)
Plants described in 1801
Natural history of the Channel Islands of California
Natural history of the San Francisco Bay Area
Natural history of the Santa Monica Mountains
Natural history of the Transverse Ranges
Plants used in Native American cuisine
Pre-Columbian California cuisine
Trees of Mediterranean climate
Garden plants of North America
Drought-tolerant trees
Ornamental trees
Oaks of Mexico