The Southern California black walnut grows well throughout sunny and semi-shaded areas within the Inland Empire and with normal winter rainfall and moderate amounts of summer water. Regular deep watering is recommended from spring through fall. It should be noted there are several winter months marked by an asterisk (*) when rains can provide sufficient moisture and irrigation is not needed. The high and low range of moisture indicates it can grow with varying amounts of water; higher amounts of water will result in stronger nut production and summer foliage character.
| |
Jan* |
Feb* |
Mar* |
Apr |
May |
Jun |
Jul |
Aug |
Sep |
Oct |
Nov* |
Dec* |
| Runs per Month |
0x to 3x |
0x to 3x |
0x to 3x |
2x to 3x |
1x to 2x |
1x to 2x |
1x to 2x |
1x to 2x |
1x to 2x |
2x to 3x |
0x to 3x |
0x to 3x |
| Inches per Run |
1″ |
1″ |
1″ |
1″ |
1″ |
1″ |
1″ |
1″ |
1″ |
1″ |
1″ |
1″ |
| |
| Inches per Month |
0″ to 3″ |
0″ to 3″ |
0″ to 3″ |
2″ to 3″ |
1″ to 2″ |
1″ to 2″ |
1″ to 2″ |
1″ to 2″ |
1″ to 2″ |
2″ to 3″ |
0″ to 3″ |
0″ to 3″ |
Range of supplemental summer water: 9"-16"
Range of supplemental winter water: 0"-15"
| |
0″-3″ |
0″-3″ |
0″-3″ |
2″-3″ |
1″-2″ |
1″-2″ |
1″-2″ |
1″-2″ |
1″-2″ |
2″-3″ |
0″-3″ |
0″-3″ |
| |
Jan* |
Feb* |
Mar* |
Apr |
May |
Jun |
Jul |
Aug |
Sep |
Oct |
Nov* |
Dec* |
For more information on how to use this Irrigation Schedule and Graph, follow this link.
For information how to calculate your irrigation system’s schedule and precipitation rate, please follow this link.
Prune when dormant in winter as needed. Walnuts exude a chemical that makes it difficult for most other plants to grow underneath them. Compatible native plants that grow well under walnuts include Oregon grape (Berberis), snowberry (Symphoricarpos), Douglas Iris (Iris douglasiana), evergreen or Catalina perfume current (Ribes viburnifolium), and hummingbird sage (Salvia spathacea) (3). Southern California black walnuts can be pruned as a multi-trunk or single trunk tree (S).
References
