Quercus oblongifolia, commonly known as the Mexican blue oak or Sonoran blue oak, is an evergreen

Evergreen

In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.There are many different kinds of evergreen plants, both trees and shrubs...

 small tree or large shrub in the white oak group. It is endemic to the south central montane regions of North America.

Distribution

This oak is common in high grassland

Grassland

Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...

s, canyon

Canyon

A canyon or gorge is a deep ravine between cliffs often carved from the landscape by a river. Rivers have a natural tendency to reach a baseline elevation, which is the same elevation as the body of water it will eventually drain into. This forms a canyon. Most canyons were formed by a process of...

s and mesa

Mesa

A mesa or table mountain is an elevated area of land with a flat top and sides that are usually steep cliffs. It takes its name from its characteristic table-top shape....

s in Texas

Texas

Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

, Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

 and New Mexico

New Mexico

New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...

 and in the states of Baja California Sur

Baja California Sur

Baja California Sur , is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. Before becoming a state on October 8, 1974, the area was known as the South Territory of Baja California. It has an area of , or 3.57% of the land mass of Mexico and comprises...

, Chihuahua, Coahuila

Coahuila

Coahuila, formally Coahuila de Zaragoza , officially Estado Libre y Soberano de Coahuila de Zaragoza is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico...

 and Sonora

Sonora

Sonora officially Estado Libre y Soberano de Sonora is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided into 72 municipalities; the capital city is Hermosillo....

 in Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

.

Description

The Mexican blue oak is a small evergreen tree growing five to eight metres tall with a rounded crown. At higher elevations it is typically a large shrub. The trunk is up to half a metre 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 two centimetres long and lodged in scaly, bowl-shaped cups about one third the length of the nut.

Habitat

This oak is common at elevations of 1200 to 1800 metres. 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 (Quercus arizonica

Quercus arizonica

Quercus arizonica, the Arizona White Oak, is found dominantly in Arizona, southwest New Mexico, northeast Sonora and Chihuahua, all Madrean Sky Islands associated regions. It is a long-lived oak in the family Fagaceae, native to eastern North America...

) and Emory oak (Quercus emoryi). It is an important constituent of pinyon-juniper

Pinyon-juniper woodland

A Pinyon-juniper woodland is a forest type characteristic of many parts the Western United States, often in higher elevations of desert ecoregions.-Locations:...

 communities. where it grows in association with species of pine and juniper, Arizona rosewood (Vauquelinia californica

Vauquelinia californica

Vauquelinia californica, commonly known as Arizona Rosewood, is an evergreen species within the rose family Rosaceae. This shrub or tree species is found in the southwestern United States, mostly Arizona, and parts of the cordillera mountain ranges in Baja California and extreme northern Baja...

), shrubby buckwheat (Eriogonum wrightii

Eriogonum wrightii

Eriogonum wrightii is a species of wild buckwheat known by the common names bastardsage and Wright's buckwheat. It is native to the Southwestern United States, California, and Northwest Mexico, where it grows in many plant communities, such as chaparral, in rocky habitats from mountains to...

), catclaw mimosa (Mimosa aculeaticarpa), bullgrass (Muhlenbergia emersleyi), plains lovegrass (Eragrostis intermedia), fendlerbush (Fendlera rupicola

Fendlera

Fendlera is a genus of shrubs in the Hydrangeaceae. They are most commonly known as fendlerbush. The name fendlerbush is also used for the closely related genus Fendlerella....

) and wolftail (Lycurus phleoides).