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Southern California Black Walnut
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Juglans californica
  

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About Southern California Black Walnut (Juglans californica) Juglans californica, the California Black Walnut, also called the California Walnut, or the Southern California Black Walnut, is a large shrub or small tree (up to 30 feet tall) endemic to California. Some authorities (e.g. the California Native Plant Society) combines this species with J. hindsii. This article uses the The Jepson Manual convention of species,. Juglans californica, generally found in the southern half of the state, 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, pinnately compound leaves with 11-19 lance-shaped 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 Chumash Indians of the Channel Islands of California eat the nuts, however, they are not grown commercially for this purpose. A recent molecular analysis suggests that J. californica is sister to the remaining black walnuts (Rhysocaryon).

This is a great choice for wildlife gardens and especially for attracting birds, which eat the nuts and like to nest in the branches. Unfortunately, Juglans californica is now endangered in large parts of the southern portion of its natural range due to continued development. Hopefully native gardeners in southern California will help restore this important part of the ecosystem. Best to plant near an irrigated area, or naturally moister areas such as a stream bed, seep or canyon bottom. Toxins in walnut seeds will typically prevent other plants from growing under this tree, so don't try to put understory plants too near this tree.
Plant Description
Plant Type
Tree

Max. Height
15 - 30 ft (4.6 - 9.1 m)

Max. Width
5 - 20 ft (1.5 - 6.1 m)

Form
Rounded

Growth Rate
Moderate

Dormancy
Winter Deciduous

Leaves
Large, pinnately compound leaves with 11-19 lance-shaped leaflets with toothed margins and no hair in the vein angles

Flower Color
Yellow

Flowering Season
Spring
Spring
Summer
Fall
Winter


Native Status
Natural Setting
Site Type
Slopes, canyons, valleys, often near stream beds or washes

Sun
Sun, Part Shade

Elevation ?
-1' - 6720'

Annual Precip. ?
5.8" - 70.7"

Summer Precip. ?
0.16" - 2.61"

Coldest Month ?
38.0° F - 56.8° F

Hottest Month ?
62.9° F - 85.5° F

Humidity ?
0.09 vpd - 36.34 vpd

Soil Description
Adaptable

Soil PH
6 - 7

Drainage
Fast, Medium, Slow

Cold Tolerance(° F)
Tolerates cold to 20 - 25° F

Sunset Zones ?
4, 5, 6, 7*, 8, 9, 10, 11, 14*, 15*, 16*, 17*, 18*, 19*, 20*, 21*, 22*, 23*, 24*

Wildlife Attracted
Very important wildlife plant - attracts many birds and small animals. Walnuts are an important food source.

Landscaping Information
Water Requirement ?
Moderate - High
Extremely Low
Very Low
Low
Moderate - High


Popularity
Moderately Popular

Max. Summer Water ?
No Summer Water, 1x/month
No Summer Water
1x/month
2x/month
3x/month
1/week
Keep moist


Propagation ?
For propagating by seed: 22.5 wks. stratification ( USDA Forest Service 1974). Some fresh seeds may need only 2-3 mos.; thus germinating seeds should be removed and planted at periodic inspections.

Common uses
Bank Stabilization, Deer Resistant, Bird Gardens

Nursery Availability
Commonly Available

Other Names
Botanical Names
Juglans californica var. californica


Sources include: Wikipedia. All text shown in the "About" section of these pages is available under the Creative Commons Attribution-ShareAlike License. Plant observation data provided by the participants of the California Consortia of Herbaria, Sunset information provided by Jepson Flora Project. Propogation from seed information provided by the Santa Barbara Botanical Garden from "Seed Propagation of Native California Plants" by Dara E. Emery. Sources of plant photos include CalPhotos, Wikimedia Commons, and independent plant photographers who have agreed to share their images with Calscape. Other general sources of information include Calflora, CNPS Manual of Vegetation Online, Jepson Flora Project, Las Pilitas, Theodore Payne, Tree of Life, The Xerces Society, and information provided by CNPS volunteer editors, with special thanks to Don Rideout. Climate data used in creation of plant range maps is from PRISM Climate Group, Oregon State University, using 30 year (1981-2010) annual "normals" at an 800 meter spatial resolution.

Links:   Jepson eFlora Taxon Page  CalPhotos  Wikipedia  Calflora

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