Oak trees of California

Oak trees of California by J. Zimmerman, Ph.D.

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Oaks are beloved trees of the open landscape of California, where they create drought-tolerant islands of shade and coolness. What kinds do we have, and where can you see them?

Buy Oaks of North America by Howard A. Miller, Samuel H. Lamb. An excellent short guide to North American oaks. Other Books on Oaks.

Remarkable Trees of the World by Thomas Pakenham. Great treasury of 60 trees of unusually strong personality. Photographed in North America, Mexico, Europe, Japan, other parts of Asia, Africa, Australia, and New Zealand.

	Deforesting the Earth: From Prehistory to Global Crisis by Michael Williams.
Books read.	Current hot books on trees and forests.
Ecology. Evolution notes.	Trees of North American. Trees of the American Pacific Northwest.

Oak Trees (Quercus).

Oaks in California are often a "keystone" species, providing habitat for hundreds or even thousands of other species. They profoundly influence the surrounding landscape.

See below for:

• How to recognize an Oak Tree.
• Where can you see Oak Trees.
• Some Fun Facts.
• Books on Oaks.

How to recognize an Oak Tree?

Appearance.

Oaks are beloved trees of the open landscape of California, where they create drought-tolerant islands of shade and coolness.

• Oaks are relatively broad for their height.
• They have hard, strong wood.
• This supports their spreading branches and leads to their unusually wide profiles.
• They are robust and solid trees.

Acorns.

The fruit of an oak is the acorn, a one-seed nut fixed in a woody cup. The acorn and its cup have these features:

• The nut has a thick shell with a large, pale circle at its base where it attached to the acorn cup.
• The length of the ripe acorns varies between species of oaks, as does the ratio of length-to-width.
• The acorn cup is formed by overlapping scales.
• The thickness of the acorn cup varies between species of oaks, as does the ratio of its length to the length of the acorn.

Leaves.

The leaves of an oak are usually deciduous, or evergreen in warmer climates. Oak leaves have these features:

• Usually the leaves are alternate in five rows.
• Often they are short-stalked and strongly veined.
• Leaf edges are toothed or lobed or straight. A single tree often shows a variety of leaves.

Flowers.

• Male and female flowers are on the same plant, often the same twig.
• Small, green flowers in early spring just before the leaves.
• Male flowers often cluster in slender, drooping catkins.
• Female flowers are at leaf bases, with a cup of overlapping scales.

Where can you see Oak Trees in California.

Oaks are widespread throughout California. The following species are likely to be seen in these regions:

1. Coastal ranges.
   • coast live oak (Quercus agrifolia).
   • canyon live oak (Quercus chrysolepsis).
   • blue oak (Quercus douglasii).
   • Oregon white oak (Quercus garryana).
2. Central valleys.
   • valley oak (Quercus lobata).
3. Sierra foothills.
   • California black oak (Quercus kelloggii).
   • valley oak (Quercus lobata).
4. Sierra Nevada.
   • interior live oak (Quercus wislizenii).
   • California black oak (Quercus kelloggii).
   • blue oak (Quercus douglasii).
   • canyon live oak (Quercus chrysolepsis).
5. Southwest.
   • Engelmann oak (Quercus engelmannii)

Fun facts on oak trees.

• Oaks grow in various environments including riverbank, woodland, chaparral, and moist prairie.
• 20 species of oak are native to California. This is about a third of the roughly 60 species native to the USA.
• Worldwide there are 500-to-600 species of oak.
• Half of California's native oak species are trees. A third are shrubs. The rest can be shrub-like or tree-like.
• Leaves can be:
  • Winter-deciduous.
  • Drought-deciduous.
  • Evergreen.
• Its fruit, the acorn, is an ovoid nut that develops from the ovary of a single female flower. It is held in a scaly cup.
• Pollen-bearing flowers are small, drooping catkins. An oak tree can have 100,000 or more male flowers, to provide wind-spread pollen.
• Seed-bearing flowers are solitary or clustered.
• Oaks are the genus Quercus.
• Quercus is a Latin name derived from two Celtic words: quer (meaning "fine") and cuez (meaning "tree").
• Oak trees, with chestnuts and beeches, are in the Beech (Fagaceae) family.

Books on Oaks.

Buy Oaks of North America by Howard A. Miller, Samuel H. Lamb. An excellent short guide to North American oaks. Rich with facts to help the amateur and the professional botanist, the book teaches the reader not only how to identify oaks, but so much about them.

• Oaks of California by Pamela Muick, et al. Superb photographs and text.
• The Life of an Oak by Glenn Keator, Susan Bazell (Illustrator). One of the best books about the oaks of the world.
• For the science-minded child: Oaks Tree by Gordon Morrison. Engaging text and margin notes edge the watercolor paintings and meticulous pencil drawings.
• Oak Tree (Webs of Life) by Paul Fleisher, Jean Cassels. (Ages 9-12.)
• The Gift of the Tree by Alvin Tresselt, Henri Sorensen (Illustrator). (Ages 4-8.)

Resources - Related pages.

• Home and List of Articles.
• Pines: Introducing Pines, Pine Fun Facts, How to Names Pines.
• Got Conifer -- How You Can Tell What Kind of Conifer You Have..

Glossary pages: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z.

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Copyright © 2001-2006 by J. Zimmerman.