Engelmann Oak
Encyclopedia
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
.
growing to 10 m tall, generally evergreen
, but may be drought-deciduous
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, 3-6 cm long and 1-2 cm broad, of a blue-green color, and may be flat or wavy, with smooth margins. The flower
s are catkin
s; the fruit
is an acorn
1.5-2.5 cm 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.
in eastern Los Angeles County through the Santa Ana Mountains
of Orange County
and the western foothills and mesas of the Peninsular Ranges
in Riverside and San Diego counties, extending into the Sierra Juárez
and Sierra San Pedro Mártir
ranges of northern Baja California. They are generally found in savanna
s and woodland
s above the dry coastal plain
, but below the 1300 meters (4200 ft) elevation where colder winters prevail. The Engelmann Oak has a smaller range than most California oaks, and suburban sprawl in the San Gabriel Valley
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
, near Murrieta
in Riverside County, and on Black Mountain
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
. The Engelmann Oak is most closely related to the Arizona White Oak
(Q. arizonica) and Mexican 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 later isolated from its closest relatives to the east by the drying of the southwestern deserts.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
in the white oak section Quercus sect. Quercus, native to Southern California
Southern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...
and northwestern Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, 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
It is a small treeTree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
growing to 10 m tall, generally 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...
, but may be drought-deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
during the hot, dry local summers, and has a rounded or elliptical canopy. The bark is thick, furrowed, and light gray-brown. The leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
are leathery, 3-6 cm long and 1-2 cm broad, of a blue-green color, and may be flat or wavy, with smooth margins. The flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s are catkin
Catkin
A catkin or ament is a slim, cylindrical flower cluster, with inconspicuous or no petals, usually wind-pollinated but sometimes insect pollinated . They contain many, usually unisexual flowers, arranged closely along a central stem which is often drooping...
s; the fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
is an acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...
1.5-2.5 cm 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
Engelmann Oak ranges from the foothills of the San Gabriel MountainsSan Gabriel Mountains
The San Gabriel Mountains Range is located in northern Los Angeles County and western San Bernardino County, California, United States. The mountain range lies between the Los Angeles Basin and the Mojave Desert, with Interstate 5 to the west and Interstate 15 to the east...
in eastern Los Angeles County through the Santa Ana Mountains
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 36 mi southeast of the Los Angeles Basin largely along the border between Orange and Riverside counties.- Geography :The range starts in the...
of Orange County
Orange County, California
Orange County is a county in the U.S. state of California. Its county seat is Santa Ana. As of the 2010 census, its population was 3,010,232, up from 2,846,293 at the 2000 census, making it the third most populous county in California, behind Los Angeles County and San Diego County...
and the western foothills and mesas of the Peninsular Ranges
Peninsular Ranges
The Peninsular Ranges are a group of mountain ranges, in the Pacific Coast Ranges, which stretch from southern California in the United States to the southern tip of Mexico's Baja California peninsula; they are part of the North American Coast Ranges that run along the Pacific coast from Alaska...
in Riverside and San Diego counties, extending into the Sierra Juárez
Sierra Juárez
Sierra de Juárez is a mountain range on the Baja California Peninsula, of Baja California, Mexico. It is part of the Peninsular Ranges. The Laguna Mountains of California lie to the north and the Sierra San Pedro Mártir lies to the south....
and Sierra San Pedro Mártir
Sierra San Pedro Mártir
Sierra de San Pedro Mártir is a mountain range that is one of the Peninsular Ranges of the Baja California peninsula, Mexico. At , the highest peak is the Picacho del Diablo, also known as Cerro de la Encantada or Picacho la Providencia...
ranges of northern Baja California. They are generally found in savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
s and woodland
Woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...
s above the dry coastal plain
Coastal plain
A coastal plain is an area of flat, low-lying land adjacent to a seacoast and separated from the interior by other features. One of the world's longest coastal plains is located in eastern South America. The southwestern coastal plain of North America is notable for its species diversity...
, but below the 1300 meters (4200 ft) elevation where colder winters prevail. The Engelmann Oak has a smaller range than most California oaks, and suburban sprawl in the San Gabriel Valley
San Gabriel Valley
The San Gabriel Valley is one of the principal valleys of Southern California, United States. It lies to the east of Los Angeles, to the north of the Puente Hills, to the south of the San Gabriel Mountains, and west of the Inland Empire. It derives its name from the San Gabriel River that flows...
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
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 to the northeast, and Temecula to the southeast.The Santa Rosa Plateau Ecological...
, near Murrieta
Murrieta, California
Murrieta has a Mediterranean climate or Dry-Summer Subtropical . Murrieta has plenty of sunshine throughout the year, with an average of 263 sunshine days and 35 days with measurable precipitation annually....
in Riverside County, and on Black Mountain
Black Mountain, San Diego County, California
Black Mountain is a summit in the Cleveland National Forest of the Peninsular Ranges in eastern San Diego County, California, north of Ramona. The peak is measured at , and is sometimes referenced as Big Black Mountain to distinguish it from the smaller Rancho Peñasquitos Black Mountain Open Space...
near Ramona
Ramona, California
Ramona is a census-designated place in San Diego County, California. The population was 20,292 at the 2010 census.The term Ramona also refers to an unincorporated community that includes both the Ramona CDP and the adjacent CDP of San Diego Country Estates CDP...
in San Diego County.
Fossil evidence shows that Engelmann Oaks once had a wider range, extending through what is now the Mojave
Mojave Desert
The Mojave Desert occupies a significant portion of southeastern California and smaller parts of central California, southern Nevada, southwestern Utah and northwestern Arizona, in the United States...
and Sonoran
Sonoran Desert
The Sonoran Desert is a North American desert which straddles part of the United States-Mexico border and covers large parts of the U.S. states of Arizona and California and the northwest Mexican states of Sonora, Baja California, and Baja California Sur. It is one of the largest and hottest...
deserts into eastern California and 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...
. The Engelmann Oak is most closely related to the Arizona White Oak
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...
(Q. arizonica) and Mexican Blue Oak
Quercus oblongifolia
Quercus oblongifolia, commonly known as the Mexican blue oak or Sonoran blue oak, is an evergreen small tree or large shrub in the white oak group...
(Q. oblongifolia), which are native to the subtropical pine-oak woodlands
Madrean pine-oak woodlands
The Madrean pine-oak woodlands are subtropical woodlands found in the mountains of Mexico and the southwestern United States.The Madrean pine-oak woodlands are found at higher elevations in Mexico's major mountain ranges, the Sierra Madre Occidental, the Sierra Madre Oriental, the Trans-Mexican...
of Arizona and northern Mexico. The Engelmann Oak is considered to be the northernmost species of subtropical oak, which was later isolated from its closest relatives to the east by the drying of the southwestern deserts.