''Quercus engelmannii'', the Engelmann oak or Pasadena oak, is a

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...

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 ' ...

section (''Quercus'' sect. ''Quercus''), native to

southern California Southern California (commonly shortened to SoCal) is a geographic and cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most populous urban ...

and northwestern

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

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 Guate ...

Description

''Quercus engelmannii'' is a small

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

growing to tall, generally

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 ...

, but may be drought-

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, a ...

during the hot, dry local summers, and has a rounded or elliptical canopy. The bark is thick, furrowed, and light gray-brown. The leaves are leathery, long and broad, of a blue-green color, and may be flat or wavy, with smooth margins. The

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

s are

catkin A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind- pollinated ( anemophilous) but sometimes insect-pollinated (as in '' Salix''). They contain many, usually unisexual flowers, arra ...

s; the

fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in partic ...

is an

acorn The acorn, or oaknut, is the nut of the oaks and their close relatives (genera '' Quercus'' and ''Lithocarpus'', in the family Fagaceae). It usually contains one seed (occasionally two seeds), enclosed in a tough, leathery shell, and bo ...

long, maturing 6–8 months after pollination. The wood is dark brown and strong, but tends to warp and split upon drying, and is of low value as timber.

Distribution

The Engelmann oak ranges from the foothills of the

San Gabriel Mountains The San Gabriel Mountains ( es, Sierra de San Gabriel) are a mountain range located in northern Los Angeles County and western San Bernardino County, California, United States. The mountain range is part of the Transverse Ranges and lies between ...

in eastern

Los Angeles County Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the most populous county in the United States and in the U.S. state of California, with 9,861,224 residents estimated as of 2022. It is th ...

through the

Santa Ana Mountains The Santa Ana Mountains are a short peninsular mountain range along the coast of Southern California in the United States. They extend for approximately southeast of the Los Angeles Basin largely along the border between Orange and Riverside ...

Orange County Orange County most commonly refers to: *Orange County, California, part of the Los Angeles metropolitan area Orange County may also refer to: U.S. counties *Orange County, Florida, containing Orlando *Orange County, Indiana *Orange County, New ...

and the western foothills and mesas of the

Peninsular Ranges The Peninsular Ranges (also called the Lower California province) are a group of mountain ranges that stretch from Southern California to the southern tip of the Baja California peninsula; they are part of the North American Coast Ranges, whic ...

in Riverside and

San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United States ...

counties, extending into the Sierra Juárez and

Sierra de San Pedro Mártir Sierra de San Pedro Mártir ( Kiliwa: ʔxaal haq, en, mountains of Saint Peter the Martyr) is a mountain range located within southern Ensenada Municipality and southern Baja California state, of northwestern Mexico. It is a major mountain ran ...

ranges of northern Baja California. It is generally found in

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

s and

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the '' plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...

s above the dry

coastal plain A coastal plain is flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and a piedmont area. Some of the largest coastal plains are in Alaska and the southeastern United States. The Gulf Co ...

, but below the elevation where colder winters prevail. The Engelmann oak has a smaller range than most California oaks, and suburban sprawl in the

San Gabriel Valley The San Gabriel Valley ( es, Valle de San Gabriel) is one of the principal valleys of Southern California, lying immediately to the east of the eastern city limits of the city of Los Angeles, and occupying the vast majority of the eastern part ...

has eliminated the oaks from most of the northern part of the range. The largest remaining stands of Engelmann oaks are on the

Santa Rosa Plateau The Santa Rosa Plateau is an upland plateau and southeastern extension of the Santa Ana Mountains in Riverside County, southern California. It is bounded by the rapidly urbanizing Inland Empire cities of Murrieta and Temecula to the northeast and ...

, near

Murrieta Murrieta is a city in southwestern Riverside County, California, United States. The population of Murrieta was 110,949 as of the 2020 census. Murrieta experienced a 133.7% population increase between 2000 and 2010, making Murrieta one of the f ...

in Riverside County, and on

Black Mountain Black Mountain may refer to: Places Australia * Black Mountain (Australian Capital Territory), a mountain in Canberra * Black Mountain, New South Wales, a village in Armidale Regional Council, New South Wales * Black Mountain, Queensland, a loca ...

near Ramona in San Diego County. Fossil evidence shows that Engelmann oaks once had a wider range, extending through what is now the Mojave and Sonoran deserts into eastern California and

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a U.S. state, state in the Southwestern United States. It is the list of U.S. states and territories by area, 6th largest and the list of U.S. states and territories by population, 14 ...

. The Engelmann oak is most closely related to the

Arizona white oak ''Quercus arizonica'', the Arizona white oak, is a North American tree species in the beech family. It is found in Arizona, New Mexico, western Texas, Sonora, Chihuahua, Coahuila, Sinaloa, and Durango. Description The Arizona white oak is one ...

''(Q. arizonica)'' and Arizona blue oak ''(Q. oblongifolia)'', which are native to the subtropical pine-oak woodlands of Arizona and northern Mexico. The Engelmann oak is considered to be the northernmost species of subtropical oak, which was isolated from its closest relatives to the east by the drying of the southwestern deserts.

References

External links

Catalogue of Life: Quercus engelmannii
* {{Taxonbar, from=Q3009480 engelmannii Flora of California Trees of Baja California Natural history of the California chaparral and woodlands Natural history of the Peninsular Ranges Trees of Mediterranean climate Garden plants of North America Drought-tolerant trees Ornamental trees Plants described in 1889 Oaks of Mexico