''Juglans californica'', the California black walnut, also called the California walnut, or the Southern California black walnut, is a large shrub or small tree (about ) of the walnut family,

Juglandaceae The Juglandaceae are a plant family known as the walnut family. They are trees, or sometimes shrubs, in the order Fagales. Members of this family are native to the Americas, Eurasia, and Southeast Asia. The nine or ten genera in the family have ...

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the Central Valley and the Coast Range valleys from Northern to Southern California.

Distribution

''Juglans californica'' is generally found in the valleys and adjacent slopes of the

California Coast Ranges The Coast Ranges of California span from Del Norte County, California, Del Norte or Humboldt County, California, south to Santa Barbara County, California, Santa Barbara County. The other three coastal California mountain ranges are the Trans ...

Transverse Ranges The Transverse Ranges are a group of mountain ranges of Southern California, in the Pacific Coast Ranges physiographic region in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie within Santa Ba ...

, and

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 Pacific Coast Range ...

. It grows as part of mixed woodlands, and also on slopes and in valleys wherever conditions are favorable. It is threatened by development and

overgrazing Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, game reserves, or nature ...

. Some native stands remain in urban

Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...

in the

Santa Monica Mountains The Santa Monica Mountains are a coastal mountain range in Southern California, next to the Pacific Ocean. It is part of the Transverse Ranges. The Santa Monica Mountains National Recreation Area encompasses this mountain range. Because of its p ...

Hollywood Hills The Hollywood Hills is a residential neighborhood in the central region of Los Angeles, California. It borders Studio City, Universal City and Burbank on the north, Griffith Park on the north and east, Los Feliz on the southeast, Hollyw ...

, and Repetto Hills. ''J. californica'' grows in

riparian A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...

woodlands, either in single species stands or mixed with California's oaks (''

Quercus An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

'' spp.) and cottonwoods (''

Populus fremontii ''Populus fremontii'', commonly known as Frémont's cottonwood, is a cottonwood (and thus a poplar) native to riparian zones of the Southwestern United States and northern through central Mexico. It is one of three species in ''Populus'' sect ...

''). Climate model predictions indicate that *Juglans californica* may expand its range northward in response to warmer and drier conditions, potentially occupying areas currently inhabited by the endangered *Juglans hindsii* (Northern California black walnut).

Description

''Juglans californica'' can be either a large shrub with 1–5 trunks, or a small, single-trunked tree. The main trunk can fork close to the ground, making it look like two trees that have grown together, then diverged. It has thick bark, deeply channeled or furrowed at maturity. It has large,

pinnate Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, and ...

ly compound leaves with 11–19

lanceolate The following terms are used to describe leaf plant morphology, morphology in the description and taxonomy (biology), taxonomy of plants. Leaves may be simple (that is, the leaf blade or 'lamina' is undivided) or compound (that is, the leaf blade ...

leaflets with toothed margins and no hair in the vein angles. It has a small hard nut in a shallowly grooved, thick shell that is difficult to remove. The tallest ''Juglans californica'' trees can reach up to 11 meters in height, though only about 10% of the population exceeds 5 meters.

Uses

Food

The nuts are edible and are eaten by the

Chumash people The Chumash are a Native Americans in the United States, Native American people of the central and southern coastal regions of California, in portions of what is now Kern County, California, Kern, San Luis Obispo County, California, San Luis O ...

of the

Channel Islands of California The Channel Islands () are an eight-island archipelago located within the Southern California Bight in the Pacific Ocean, off the coast of California. They define the Santa Barbara Channel between the islands and the California mainland. The ...

and

Ventura County Ventura County () is a county located in the southern part of the U.S. state of California. As of the 2020 census, the population was 843,843. The largest city is Oxnard, and the county seat is the city of Ventura. Ventura County comprises ...

as well as by the Tongva of Los Angeles County. They are not grown commercially as food.

Cultivation

''Juglans californica'' is cultivated throughout California to support the walnut industry, used as a rootstock in English walnut orchards. It is also cultivated as an ornamental tree where it is planted in California native plant,

xeriscape Xeriscaping is the process of landscaping, or gardening, that reduces or eliminates the need for irrigation. It is promoted in regions that do not have accessible, plentiful, or reliable supplies of fresh water and has gained acceptance in other ...

, and

wildlife habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

gardens and

natural landscaping Natural landscaping, also called native gardening, is the use of native plants including trees, shrubs, groundcover, and grasses which are local to the geographic area of the garden. Benefits Maintenance Natural landscaping is adapted to t ...

in California, and in Hawaii.

Taxonomy

Some authorities (e.g. the

California Native Plant Society The California Native Plant Society (CNPS) is a California environmental non-profit organization (501(c)(3)) that seeks to increase understanding of California's native flora and to preserve it for future generations. The mission of CNPS is to c ...

) combine this species with ''

Juglans hindsii ''Juglans hindsii'', commonly called the Northern California black walnut and Hinds's black walnut, is a species of walnut tree native to the western United States (California and Oregon). It is commonly called claro walnut by the lumber industry ...

''. On the other hand, a 2007 molecular analysis of the genus suggests ''J. californica'' is sister to the remaining black walnuts (section Rhysocaryon). This article follows the conventions of ''The Jepson Manual''.Juglans hindsii Jeps. ex R. E. Sm.
/ref>

References

External links

Jepson Manual Treatment – ''Juglans californica''''Juglans californica''
– U.C. Photo gallery
Interactive Distribution Map for ''Juglans californica''
{{Taxonbar, from=Q890824 californica Endemic flora of California Trees of Northern America Natural history of the California chaparral and woodlands Natural history of the California Coast Ranges Natural history of the Central Valley (California) Natural history of the Peninsular Ranges Natural history of the San Francisco Bay Area Natural history of the Santa Monica Mountains Natural history of the Transverse Ranges Trees of Mediterranean climate Edible nuts and seeds Plants used in Native American cuisine Pre-Columbian California cuisine Garden plants of North America Drought-tolerant plants Ornamental trees