Valley oak

Description

Quercus lobata, commonly called the valley oak or roble, grows into the largest of North American oaks. It is endemic to California, growing in interior valleys and foothills from Siskiyou County to San Diego County. Mature specimens may attain an age of up to 600 years. This deciduous oak requires year-round access to groundwater. Its thick, ridged bark is characteristic and resembles alligator hide. The valley oak's deeply lobed leaves assist in identification. The valley oak may surpass 30 meters (98 feet) in height, with a sturdy trunk possibly exceeding 3 m (10 ft) in diameter. The "Henley Oak", in Covelo, California, is the tallest known valley oak, at 47 m (153 ft). The branches have an irregular, spreading and arching appearance that produce a profound leafless silhouette in the clear winter sky. During autumn, the leaves turn a yellow to light orange color but become brown later in the season. In advancing age, the branches assume a drooping characteristic. The tree's pewter-colored rippled bark adds to the attractive aesthetic of this species. Typically, the leaves are 5–10 centimeters (2–4 inches) long and are roundly and deeply lobed. The leaf width is approximately one half its length. Each leaf is matte green with an underneath pale green appearance; moreover, the leaf is covered with abundant soft fuzz, yielding an almost velvety feeling. When a fresh leaf is rubbed or broken, an aromatic scent is exuded, evoking a forest odor. The wood is a dull brown approaching yellow. The acorns are medium to dark brown and range from 2 to 3 cm (3⁄4 to 1+1⁄4 in) in length. The caps have deep stippling and are found most often as singlets, but occasionally as doublets. The acorns ripen from October to November. Viable acorns germinate in their first winter, and none remain by mid-winter. Valley oak tolerates cool wet winters and hot dry summers, but requires abundant water. It is most abundant in rich deep soils of valley floors below 600 meters (2000 feet) in elevation. Valley oak is found in dense riparian forests, open foothill woodlands and valley savannas. Commonly associated trees are coast live oak, interior live oak, blue oak, California black walnut, California sycamore and gray pine.