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Valley oak, also known by its scientific name Quercus lobata Née and commonly called white oak or marsh oak, is a species of oak that is native to California and grows wild mainly in that state. It is a deciduous tree, meaning it sheds its leaves every year, and it is the largest oak species native to North America. Mature specimens can reach up to 98 feet (about 30 m) tall with a trunk that is 6.5 to 10 feet (roughly 2 to 3 m) in diameter.
The valley oak is so named because it usually grows in valleys and foothills, and it is an important part of the local ecosystem. Its wood is brown in color and susceptible to damage from fungus and burrowing insects. For this reason, it is rarely used for woodworking or construction purposes.
The bark of a valley oak is gray or pewter colored with deep ridges. Its leaves are 2.5 to 4 inches (about 5 to 10 cm) long, deeply lobed, dark yellow-green on top, pale grayish-green beneath and velvety in texture. The tree blooms in March to April and produces acorns in the fall. The acorns are about 2 inches (5 cm) long, with a pointy tip; a mature valley oak can produce up to 1 ton (about 907 kg) of acorns in a year. In the past, these acorns were commonly harvested by Native Americans in the region.
The valley oak can tolerate hot, dry summers and cool, wet winters, and is resistant to 7 °F (about -13°C), but it does not grow well in shaded locations. This tree prefers to grow in rich soil and is often found along river beds because it requires good access to groundwater; regular river flooding also provides the soil with more nutrients. The valley oak is a valuable species in its local habitat. Its extensive root system helps control erosion in areas prone to flooding, and the tree is a food source for deer; the acorns are eaten by other native animals and birds, such as the California ground squirrel, scrub jays and acorn woodpeckers.
This tree can be propagated from gathered acorns, but they must be planted soon after they become mature because they will not germinate if they are stored for long periods of time. It is also best to plant acorns from local trees because they may be better adapted to local conditions. Seedlings can be grown in containers or planted in the ground and need to be watered regularly so the soil does not dry out.