As the human population expands and moves westward, the majestic, massive valley oak, which gave Thousand Oaks its name, is slowly disappearing.

This member of the oak family, native only to California, commonly grows in sheltered coastal valleys and foothill areas below 2,000 feet. Once abundant in the San Fernando Valley, the valley oak (Quercus lobata) is today concentrated in areas such as Calabasas, Agoura, Westlake Village and Thousand Oaks.

Botanists and environmentalists attribute the tree's demise mainly to destruction by developers. But grazing farm animals also have contributed to the disappearance of many valley oaks over the years by eating the trees' seedlings.

Environmental groups such as the San Fernando Valley-based Oak Tree Coalition have successfully lobbied local governments to pass laws protecting the dwindling number of valley oaks, many of which are hundreds of years old. Los Angeles County and the cities of Los Angeles, Agoura Hills and Thousand Oaks have adopted ordinances making it illegal to destroy oaks without a permit.

Five years ago, state officials classified an area of Liberty Canyon in Malibu Creek State Park as a natural preserve to protect the stately trees.

The valley oak, also known as the California white oak, attains heights up to 125 feet. It grows in soil that is deep and rich. The tree's branches are large, wide-spreading and inviting to climbing children. Its bark is thick, with cubelike checks. It makes poor lumber and is used mainly for firewood.

The oak's dark green leaves are 2 1/2 to four inches long and have seven to 11 rounded, deeply cut lobes. The leaves have gray to yellow hairs on the underside. The tree's acorns taper to a point and have knobby cups.

Valley oaks pictured here can be found in Malibu Creek State Park in Agoura, at the California Botanical Garden in Thousand Oaks and dotting the hillside along Las Virgenes Road in Calabasas.

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