Quercus douglasii
Blue oak ( Quercus douglasii )
The blue oak ( Quercus douglasii ) is a species of the genus of oaks (Quercus ). It is native to California. The trivial name of Blue Oak and "Blue Oak " refers to the blue-green color of the leaves.
- 4.1 Notes and references
Description
Appearance and bark
The blue - oak grows as a deciduous tree and reaches an average growth height of 15 to 25 meters. In most cases, only one root, sometimes are few available to some strains. The scaly bark is gray. The reddish or yellowish bark of the branches is hairy, more or less dense and fluffy verkahlt occasionally in old age.
Buds and leaves
The reddish brew buds (up to 2 ) usually 3-5 mm wide - ovate to rarely nearly spherical with a length of. The bud scales are mostly bald, hairy, sometimes more or less dense fluffy and always have ciliated edges.
The alternate arranged on the branches of deciduous leaves are blue - green (hence the common name ) and divided into petiole and leaf blade. The petiole has a length of 2 to 6 mm. The leaf blade is simple with a length of usually 4 to 6 ( 2 to 8) inches and a width of usually 2 to 3 ( 1.5 to 4 ) cm obovate, elliptical, oblong or upside - lanceolate with more or less rounded, often wedge-shaped Spreitenbasis and usually rounded or rarely slightly pointed top. The leaf margin is slightly lobed or irregularly dentate, rarely smooth; the lobes are spiny or rounded. Six to ten side nerves on each side of the central nerve.
Generative features
The blue oak is monoecious getrenntgeschlechtig ( monoecious ). The flowering time is in the late winter to spring. The inconspicuous flowers are unisexual.
The solitary on a very short stalk acorns are only covered at their base by a fruit cup ( cupula ). The at a height of 5 to 10 mm and a diameter of 10 to 15 mm hemispherical to cup-shaped cupula has thin scales, which are not, or hard and uneven warty, especially near the base of the cupula. The thin-walled acorn ( nut fruit ) is spindle-shaped or nearly cylindrical with a length of 2 to 3 cm and a diameter of 1 to 1.6 cm. The seeds contain two free cotyledons ( cotyledons ).
The chromosome number is 2n = 24
Dissemination
The blue oak is native to the United States only in California, especially in the foothills of California's Central Valley and the California coastal mountains. It grows in oak woodlands, edges of chaparral and grassland at altitudes 0-1200 meters.
System
The first description of Quercus douglasii was made in 1840 by William Jackson Hooker and George Arnott Walker Arnott in The Botany of Captain Beechey 's Voyage, p 391 Quercus douglasii Hook synonyms for. & Arn. are: Quercus douglasii var ransomii ( Kellogg ) Beissner: Quercus ransomii Kellogg. Quercus douglasii Quercus belongs to the section of the subgenus Quercus in the genus Quercus.
Swell
- Kevin C. Nixon: Quercus. In: Flora of North America. Volume 3, 1997 Quercus douglasii -. Online. (Section Description, distribution and systematics)