Juglans californica Forest & Woodland Alliance
California walnut groves

USDA Ecological Section Map

Summary Information

  • Primary Life FormTree
  • Elevation150-900 m
  • State RarityS3.2
  • Global RarityG3
  • DistributionUSA: CA (NatureServe)
  • Endemic to CaliforniaYes
  • Endemic to California Floristic Province and DesertsYes
  • Date Added1995/11/01

Characteristic Species

Juglans californica is dominant or co-dominant in the tree canopy with Alnus rhombifolia, Fraxinus dipetala, Heteromeles arbutifolia, Quercus agrifolia, Quercus lobata, Salix laevigata, Salix lasiolepis, Sambucus nigra and Umbellularia californica.

Vegetation Layers

Trees < 15 m tall; canopy is open to continuous. Shrub layer is sparse to intermittent. Herbaceous layer is sparse or grassy.

Membership Rules

  • Juglans californica > 50% relative cover in the tree canopy or > 30% relative cover with Quercus agrifolia present (Keeler-Wolf and Evens 2006).


Riparian corridors, but most stands cover all hillslopes. The USFWS Wetland Inventory (1996 national list) recognizes Juglans californica as a FAC plant.

Other Habitat, Alliance and Community Groupings

MCV (1995) California walnut series
NVCS (2009) Juglans californica woodland alliance
Calveg Black walnut
Holland California walnut woodland, Walnut forest
Munz Southern oak woodland
WHR Coastal oak woodland
CDFW CA Code 72.100.00

National Vegetation Classification Hierarchy

Formation Class Mesomorphic Tree Vegetation (Forest and Woodland)
Formation Subclass Temperate Forest
Formation Warm Temperate Forest
Division Madrean Forest and Woodland
Macro Group California Forest and Woodland
Group Californian broadleaf forest and woodland