For the school in Napa County, California

Napa County, California

Napa County is a county located north of the San Francisco Bay Area in the U.S. state of California. It is coterminous with the Napa, California, Metropolitan Statistical Area. As of 2010 the population is 136,484. The county seat is Napa....

 named after Blue Oaks, see Blue Oak School

Blue Oak School

Blue Oak School is an independent school in Napa, California. The building the school is housed within was originally built in 1909 and called the Washington Primary School. In the 1950s, the building became the Napa County Offices. In 2002 the building was renovated and named Blue Oak School...

.

Quercus douglasii, the Blue Oak, is an oak

Oak

An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

 in the white oak section of the genus, Quercus sect. Quercus. It is endemic to California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 and is found in foothills

Foothills

Foothills are geographically defined as gradual increases in elevation at the base of a mountain range. They are a transition zone between plains and low relief hills to the adjacent topographically high mountains.-Examples:...

 surrounding the Central Valley

California Central Valley

California's Central Valley is a large, flat valley that dominates the central portion of California. It is home to California's most productive agricultural efforts. The valley stretches approximately from northwest to southeast inland and parallel to the Pacific Ocean coast. Its northern half is...

 of California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 and certain locations in the California Coast Ranges, USA

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It is also sometimes known as the Mountain Oak, and occasionally the Iron Oak.

Description

Quercus douglasii, the Blue Oaks, are medium-sized tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s growing up to 15–25 m tall, usually with a somewhat irregularly-shaped crown, and a trunk 0.5–1 m in diameter. The tallest recorded oak was found in southern Alameda County, at 94 ft. The bark

Bark

Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...

 is light gray with many medium-sized dark cracks; from a distance, it can appear almost white. The name Blue Oak derives from the dark blue-green tint of its leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

, which are deciduous

Deciduous

Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...

, 4–10 cm long, and entire or shallowly lobed. The blue color can be subtle but becomes much more evident when viewed next to one of the live oak

Live oak

Live oak , also known as the southern live oak, is a normally evergreen oak tree native to the southeastern United States...

s with whom it shares its range, which tend to have much greener leaves. The acorn

Acorn

The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...

s are 2–3 cm long, with a moderately sweet kernel

Nut (fruit)

A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...

, and mature in 6–7 months from pollination

Pollination

Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...

. It prefers dry soil and plenty of sunlight.

Individual Blue Oaks over 500 years old have been recorded, although most are less than 300 years old. Recent research has found several unlogged stands of Blue Oak woodlands

California oak woodland

California oak woodland is a plant community found throughout the California chaparral and woodlands ecoregion of California in the United States and northwestern Baja California in Mexico...

, suggesting that the state may harbor over 500000 acres (2,023.4 km²) of such old growth forest

Old growth forest

An old-growth forest is a forest that has attained great age , and thereby exhibits unique ecological features. An old growth forest has also usually reached a climax community...

s.

Natural hybrids between Blue Oak and the related Shrub Live Oak (Quercus turbinella), Valley Oak

Valley Oak

Quercus lobata, commonly called the Valley oak, grows into the largest of North American oaks. It is endemic to California, growing in the interior valleys and foothills. Mature specimens may attain an age of up to 600 years. This deciduous oak requires year-round access to groundwater.Its thick,...

 (Q. lobata) and Oregon White Oak

Garry Oak

Quercus garryana, the Garry Oak, Oregon White Oak or Oregon Oak, has a range from southern California to extreme southwestern British Columbia, particularly southeastern Vancouver Island and the adjacent Gulf Islands. It grows from sea level to 210 m altitude in the northern part of its range, and...

 (Q. garryana) often occur where the species grow together in the same area. Other species sympatric with the Blue oak include Canyon live oak and Pacific madrone

Pacific Madrone

Arbutus menziesii, commonly known as the Pacific Madrone, is a species of Arbutus found on the west coast of North America, from British Columbia to California...

.

Quercus douglasii is susceptible to Sudden Oak Death

Sudden oak death

Sudden Oak Death is the common name of a disease caused by the oomycete plant pathogen Phytophthora ramorum. The disease kills oak and other species of tree and has had devastating effects on the oak populations in California and Oregon as well as also being present in Europe...

 disease (Phytophthora ramorum), though less so than Tanoak

Tanoak

Tanoak, formerly known taxonomically as Lithocarpus densiflorus, was recently moved into a new genus, Notholithocarpus, based on multiple lines of evidence....

 (Lithocarpus densiflorus), or red oaks such as Coast live oak

Coast Live Oak

Quercus agrifolia, the Coast Live Oak, is an evergreen oak , native to the California Floristic Province. It grows west of the Sierra Nevada from Mendocino County, California, south to northern Baja California in Mexico. It is classified in the red oak section Quercus agrifolia, the Coast Live Oak,...

(Q. agrifolia).