Sun: Full Sun, Part Shade
Moisture: Moderate – High
Summer Irrigation Max 1x / month once established
Cold Tolerance: Tolerates cold to 20 – 25° F
Soil Drainage: Fast, Medium, Slow
Soil Description: Adaptable. Soil PH: 6 – 7
Common uses: Bank Stabilization, Deer Resistant, Bird Gardens
Companion Plants: Scrub Oak (Quercus berberidifolia), Coast Live Oak (Quercus agrifolia), Red Willow (Salix laevigata), Mountain Mahogany (Cercocarpus betuloides), Virgin’s Bower (Clematis ligusticifolia), California Wildrose (Rosa californica), Riverbank Lupine (Lupinus latifolius), Climbing Penstemon (Keckiella cordifolia), Blue Elderberry (Sambucus nigra ssp. caerulea)
Sunset Zones: 4, 5, 6, 7*, 8, 9, 10, 11, 14*, 15*, 16*, 17*, 18*, 19*, 20*, 21*, 22*, 23*, 24*
Site Type: Slopes, canyons, valleys, often near stream beds or washes
Climate: Annual Precipitation: 5.8″ – 70.7″,
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 ate 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.