Every so often I need to proclaim the beauty and benefits of having oaks on the land. California’s signature plant, they are majestic, long-lived, and hardy. But most of all, oaks offer food and shelter to so many birds and insects. They are nesting sites for owls and hawks and small cavity nesters, such as nuthatches and chickadees and the oak titmouse. Woodpeckers, jays and squirrels eat the acorns and by hiding their acorn treasures, spread the seed. All parts of the oak tree—acorns, pollen, sap and leaves-—are food sources. Oak woodlands provide habitat for over 300 species of birds, mammals, reptiles and amphibians and over 5,000 insects, including 7 species of butterflies. They are the only host plant for the beautiful California sister butterfly. Coast live oak, valley oak, Oregon oak, CA black oak, and blue oaks are the most common species in Sonoma County. Many of these oaks hybridize into new species– blue oak and Oregon oak, for example, in North Sonoma Mountain Regional Park.
Oaks thrive on winter rain and summer drought; watering under mature oaks invites pathogens and fungi to take up residence, but newly planted oaks need water until they are established. Some tips: Minimize pruning, avoid cutting the roots and paving within the root zone, or compacting the soil with foot traffic, cars or construction. Plants near or around oaks should not need supplemental water during the dry months. There are many native trees and shrubs, perennials and groundcovers that work well with oaks. For example: shrubs such as coffeeberry, snowberry, and pink-flowering currants; perennials/ groundcovers such as coral bells (Heuchera spp.), Douglas iris, low-growing manzanitas, woodland strawberry, and California fescue thrive in dry shade to part shade and do not need supplemental water. (See Appendix C: Oaks in the Landscapes in my book for more oak-friendly plants.)