Blue oak
| Blue oak | ||||||||||||
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Blue oak ( Quercus douglasii ) |
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| Quercus douglasii | ||||||||||||
| Hook. & Arn. |
The blue-oak ( Quercus douglasii ) is a plant from the genus of oak ( Quercus ). It is native to California . The common names blue oak and "blue oak" refer to the blue-green color of the leaves.
description
Appearance and bark
The blue oak grows as a deciduous tree and reaches an average height of 15 to 25 meters. Usually there is only one trunk, sometimes a few to a few trunks are present. The scaly bark is gray. The reddish or yellowish bark of the branches is hairy more or less densely and occasionally balds with age.
Buds and leaves
With a length of (2 to), the reddish-brown buds are usually 3 to 5 mm wide and ovoid to rarely almost spherical. The bud scales are mostly bare, sometimes more or less densely hairy and always have ciliate edges.
The alternate arranged on the branches leaves are blue-green (hence the common name) and petiole and leaf blade divided. The petiole has a length of 2 to 6 mm. The simple leaf blade is usually 4 to 6 (2 to 8) cm long and 2 to 3 (1.5 to 4) cm wide and is obovate, elliptical, oblong or obverse-lanceolate with more or less rounded , seldom wedge-shaped blade base and mostly rounded or seldom slightly pointed upper end. The leaf margin is slightly lobed or serrated irregularly, rarely smooth; the leaf lobes are prickly or rounded. There are six to ten lateral nerves on each side of the median nerve.
Generative characteristics
The blue oak is single sexed ( monoecious ). The flowering time is from late winter to spring. The inconspicuous flowers are unisexual.
The acorns, which stand individually on a very short stem, are only covered by a fruit cup (cupula) at their base . The cupula, which is hemispherical to cup-shaped at a height of 5 to 10 mm and a diameter of 10 to 15 mm, has thin scales that are not warty or thick and unevenly warty, especially near the base of the cupula. The thin-walled acorn ( nut fruit ) is spindle-shaped or almost 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 number of chromosomes is 2 n = 24.
distribution
The blue oak is native to the USA only in California, especially in the foothills of the California Long Valley and in the California Coast Mountains . It thrives in oak forest areas, edges of the chaparral and grasslands at altitudes between 0 and 1200 meters.
Systematics
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. synonyms for Quercus douglasii Hook. & Arn. are: Quercus douglasii var. ransomii (Kellogg) Beissner: Quercus ransomii Kellogg. Quercus douglasii belongs to the Quercus section from 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)
- Philip M. McDonald: Quercus douglasii in Silvics Manual. Volume 2: Hardwoods. at USDA Forest Service Northeastern Area . (Section Description and Distribution)
Individual evidence
- ^ A b c Philip M. McDonald: Quercus douglasii .
- ↑ a b c d e f g Kevin C. Nixon: Quercus. In: Flora of North America. Volume 3, 1997. Quercus douglasii - Online.
- ↑ First description scanned at biodiversitylibrary.org .
- ↑ Quercus douglasii at Tropicos.org. Missouri Botanical Garden, St. Louis
