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Coast Live Oak (Quercus agrifolia)
The Latin name Quercus, meaning “oak,” was thought to be derived from two Celtic words: quer, meaning fine and cuez, meaning tree. A “fine tree” hardly describes such a noble and picturesque tree as the coast live oak, Quercus agrifolia. While traveling through plains, foothills, valleys and woodlands, all natural territories of the coast live oak, I am transported to early California—a land of beauty where this tree was a prominent feature in the landscape.
This species is an evergreen native to California. Its region is west of the Sierra Nevada, from Mendocino County south to northern Baja California in Mexico. You can also find it growing on the rugged slopes of Santa Cruz and Santa Rosa Islands. Its ability to thrive along the coast makes this tree a unique species.
Mature trees may have a single or multi-branched trunk, often massive with sprawling limbs that arch gracefully towards the ground. The bark of young trees has a smooth texture and with age develops shallow fissures in its grayish colored surface. The crown is dense and broadly rounded, reaching a height of 75 feet (m) with the crown spread exceeding the height. The upper leaf surface is deep green and quite glossy with a cupped oval shape, 1 to 3 inches (cm) long. The leaves have toothed margins and feel leathery to the touch. The lower surface is paler, with hairy-tufted vein axils. In spring the fresh growth is flushed with a rosy hue. The short chartreuse catkins flowers add a graceful contrast to the dark green leaves, while the female flowers are inconspicuous. Flowering takes place from February to April. The coast live oak is monoecious and wind-pollinated.
The coast live oak is known to grow in Sunset Zones 5, 7 – 10, 12 and 14 – 24 and in
USDA Hardiness Zones 9 – 10. This species is adapted to relatively warm, wet winters and dry summers moderated by fog and cool temperatures; however, it cannot survive where the ground freezes. Exposure may ranges from full sun to partial shade. Soil type can range from clay, loam, or sand with a pH range from 5.5 to 7.5. When looking for drought tolerant as well as deer tolerant trees, consider the coast live oak. It is particularly adapted to fire. Under extreme drought this oak may go deciduous.
Quercus agrifolia is sensitive to changes in grading and drainage; in particular, avoid adding soil near the trunk when construction or landscape occurs. Be particularly careful when using artificial irrigation not to over-water and not to allow wet soil in summer where soil-borne Phytophthora diseases or Armillaria might be present. Mature trees are susceptible to oak crown and root rot fungi that decay wood in trunks and roots. Never plant an oak where another oak died from disease. Watch for aphids, beetle borers, caterpillars, coddling moths, insect galls, scales and white fly as well as powdery mildew and sooty mold.
The coast live oak is a versatile landscape tree with low maintenance. It can be used as a shade or street tree (if given ample space), park, and specimen tree. Under ideal conditions the coast live oak can live up to 250 years. Within its majestic branches these oaks will supply food, shade, shelter and protection for multiple generations of wildlife, including many birds, butterflies and various other animals. In addition, Quercus agrifolia plays a critical role to healthy ecosystems by developing soil profiles, erosion control, nutrient cycling, and sustaining air and water quality. I hope you will enjoy the aesthetic value that this oak will bring throughout a life time.
—Delia B. Juncal, San Diego Regional Urban Forests Council, Landscape Development Coordinator, Oceanside, California |
