Quercus oblongifolia, commonly known as the Mexican blue oak, Arizona blue oak, Blue live oak or Sonoran blue oak, is an

evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which ...

small tree or large shrub in the

white oak The genus ''Quercus'' contains about 500 species, some of which are listed here. The genus, as is the case with many large genera, is divided into subgenera and sections. Traditionally, the genus ''Quercus'' was divided into the two subgenera '' ...

group.

Distribution

''Quercus oblongifolia'' grows in high

grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...

canyon A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive activity of a river over geologic time scales. Rivers have a natural tenden ...

s and

mesa A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by ...

s in southwestern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

(

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

and

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

) and northwestern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

(

Baja California Sur Baja California Sur (; 'South Lower California'), officially the Free and Sovereign State of Baja California Sur ( es, Estado Libre y Soberano de Baja California Sur), is the least populated state and the 31st admitted state of the 32 federal ent ...

, Chihuahua,

Coahuila Coahuila (), formally Coahuila de Zaragoza (), officially the Free and Sovereign State of Coahuila de Zaragoza ( es, Estado Libre y Soberano de Coahuila de Zaragoza), is one of the 32 states of Mexico. Coahuila borders the Mexican states of N ...

Sinaloa Sinaloa (), officially the Estado Libre y Soberano de Sinaloa ( en, Free and Sovereign State of Sinaloa), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. It is d ...

and

Sonora Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is d ...

states). Mexican blue oak is closely related to Engelman oak "

Quercus engelmannii ''Quercus engelmannii'', the Engelmann oak or Pasadena oak, is a species of oak in the white oak section (''Quercus'' sect. ''Quercus''), native to southern California and northwestern Baja California, Mexico. Description ''Quercus engelmannii'' ...

" in Southern California. The two species may be conspecific and could be combined as one species.

Description

The Mexican blue oak is a small

tree growing 5–8'' ''metres (16–27'' ''feet) tall with a rounded crown. At higher elevations it is typically a large shrub. The trunk is up to in diameter and the bark is light gray and densely furrowed. The twigs are yellowish brown and hairless with reddish brown buds. The

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

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 long and lodged in scaly, bowl-shaped cups about one third the length of the nut.

Habitat

The Mexican blue oak is common at elevations of 1,200 to 1,800'' ''m (4,000–6,000'' ''ft). 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'', the Arizona white oak, is a North American tree species in the Fagaceae, beech family. It is found in Arizona, New Mexico, western Texas, Sonora, Chihuahua (state), Chihuahua, Coahuila, Sinaloa, and Durango. Description ...

'') and Emory oak (''

Quercus emoryi ''Quercus emoryi'', the Emory oak, is a species of oak common in Arizona (including inside Saguaro National Park), New Mexico and western Texas (including inside Big Bend National Park), United States, and northern Mexico (Sonora, Chihuahua, Co ...

''). It is an important constituent of pinyon–juniper communities. where it grows in association with species of

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accep ...

and

juniper Junipers are coniferous trees and shrubs in the genus ''Juniperus'' () of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely distributed throughout the Northern Hemisphere, from the Arcti ...

, Arizona rosewood (''

Vauquelinia californica ''Vauquelinia californica'', commonly known as Arizona rosewood, is an evergreen species of shrub or tree, in the rose family, Rosaceae. The dark brown wood streaked with red, and is hard and very heavy, a beautiful 'rosewood.' It has dense whit ...

''), shrubby buckwheat (''

Eriogonum wrightii ''Eriogonum wrightii'' is a species of Eriogonum, 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 communit ...

''), catclaw mimosa (''

Mimosa aculeaticarpa ''Mimosa aculeaticarpa'' is a species of woody shrub in the family Fabaceae. It is commonly known as the catclaw mimosa or the wait-a-minute bush, and is endemic to upland regions of Mexico and the Southwestern United States, particularly Ar ...

''), bullgrass (''

Muhlenbergia emersleyi ''Muhlenbergia'' is a genus of plants in the grass family. The genus is named in honor of the German-American amateur botanist Gotthilf Heinrich Ernst Muhlenberg (1753-1815). Many of the species are known by the common name muhly. The greatest ...

''), plains lovegrass (''

Eragrostis intermedia ''Eragrostis intermedia'' is a species of grass known by the common name plains lovegrass. It is native to North and Central America, where it is distributed from the southeastern and southwestern United States south to Costa Rica.Walsh, Roberta ...

''), fendlerbush ('' Fendlera rupicola'') and wolftail (''

Lycurus phleoides ''Lycurus'' is a small genus of New World plants in the grass family, native to North and South America. These grasses are known commonly as wolfstails. ; Species * '' Lycurus phalaroides'' Kunth - Mexico, Guatemala, Colombia, Ecuador, Peru, B ...

'').

Cultivation

Mexican 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.

References

{{Taxonbar, from=Q3414214 oblongifolia Trees of the Southwestern United States Plants described in 1853 Oaks of Mexico Flora of the Sierra Madre Occidental