Quercus oblongifolia


Quercus oblongifolia, commonly known as the Arizona blue oak, Blue live oak or Sonoran blue oak, is an evergreen small tree or large shrub in the white oak group.

Distribution

Quercus oblongifolia grows in high grasslands, canyons and mesas in Texas, Arizona and New Mexico and northwestern Mexico. Arizona blue oak is closely related to Engelman oak "Quercus engelmannii" in Southern California. The two species may be conspecific and could be combined as one species.

Description

The Arizona blue oak is a small evergreen tree growing 5–8 meters tall with a rounded crown. At higher elevations it is typically a large shrub. The trunk is up to 50 cm in diameter and the bark is light gray and densely furrowed. The twigs are yellowish brown and hairless with reddish brown buds. The leaves are small, alternate and oblong, with entire margins, leathery, bluish-green above and mid green below. The flowers appear in spring at the same time as the old leaves are being shed and new leaf growth starts. The male flowers form yellowish-green catkins and the female flowers are solitary or paired and grow in the leaf axils. The light brown acorns are ovoid or oblong, about 2 cm long and lodged in scaly, bowl-shaped cups about one third the length of the nut.

Habitat

The Arizona blue oak is common at elevations of 1200 to 1800 meters. It is often found on thin sandy soils in semi-arid regions and is the dominant species in lower open oak woodland where it grows in association with Arizona white oak and Emory oak. It is an important constituent of pinyon-juniper communities. where it grows in association with species of pine and juniper, Arizona rosewood, shrubby buckwheat, catclaw mimosa, bullgrass, plains lovegrass, fendlerbush and wolftail.

Cultivation

Arizona blue oak "Quercus oblongifolia" popularity in landscaping has been increasing in California with many plantings at Apple Park and other Bay area plantings. The fast growth and beautiful blue foliage makes selections from trees in Arizona the best for cultivation.