Gardener’s Notebook

Growing Food Near Native Oaks

native-oak

Is it possible to grow perennial food plants near native oaks? 
Yes, with the right plants and methods.

Here in Northern California, we are blessed with many stoic and picturesque native oaks. Quercus agrifolia (coastal live oak), Quercus lobata (valley oak), and Quercus douglasii (blue oak) are all found in this bioregion. While sudden oak death and other oak ailments may be a result of anthropogenic (man-made) influences, fear not: By following some simple rules and planting specially adapted native plants, you can foster life under and around your oaks.

Drip Line Denotes Microclimate

pink flowering currantOur California oaks have evolved to thrive in dry soil throughout our long summer drought. While those conditions would seem to discourage plant growth, an intact oak savanna ecosystem displays a diversity of plants growing in the “skirts” of the oak trees, due to the increased moisture present in areas around the tree where rain (and accumulated fog) drips from the branches. Called the “drip line,” this is a sweet spot for many of the oak savanna native plant species, and gardeners can put it to good use. 

In my consulting work with homeowners and on ranches, one of the main mistakes I see is that irrigation is installed too close to the drip line of the oak. This “wet feet” condition can lead to rot and disease. By choosing the right specialists for the very specific habitat around our oaks, we can achieve a full, vibrant understory that will bring hummingbirds and other wildlife right underneath the majestic trees and into view from our windows. 

Savvy Bay Area gardeners make use of the partial-shade area outside an oak’s drip line for growing edible plants like those in the list below. In this area outside the drip line, it is safe to water twice per week.  

Edibles for Oak Shade (outside drip line) 

Note: These are all “low chill” cultivars, which do well in the Bay Area. Even though we think apples and cherries need full sun, they can do well in light shade, since it tricks them into thinking the winters here are chillier than they are.

Apple: Fuji and Pink Lady
High Bush Blueberry (Vaccinium corymbosum): Sunshine Blue and Jewel 
Cherry: (Prunus avium) Royal Lee (Note: Cherries like acidic soil.)
Currants: Edible cultivars of currant do well in the light shade outside the canopy. Native currant plants are adapted to our summer drought conditions, but the food-producing cultivars of red currant (Ribes rubrum), white currant, and black currant (Ribes nigrum) need more water, so they should not be planted directly under the oak canopy. 
Raspberry (Rubus idaeus): Raspberry will tolerate light shade.
Rhubarb (Rheum rhabarbarum): another perennial food crop you can grow near your oak trees.

 Some apples can thrive in light shade, as can edible cultivars of currant (blossoms pictured above at right).

Some apples can thrive in light shade,
as can edible cultivars of currant (blossoms pictured above at right).

Dry Oak Shade Specialists (inside the drip line):  

The deep-shade zone inside the circle of the oak’s drip line is the realm of native plant oak specialists. These plants have adapted over eons to tolerate the shade of the oak as well as the intense acidity of the oak leaf duff. These plants tend to have upright growth habits, which allows them to stay above the leaf drop in autumn when the leaves can accumulate to over a foot deep. 

Try these native plants under the oak’s canopy:
These plants are drought tolerant and need water only once per week. Drip irrigation is the preferred delivery method, as it will target the new plant’s root zone without soaking the surface. If the soil is workable, these plants can be put in during the wet season. Do your part and do not irrigate directly under your oak canopy near the trunk/root crown.  

Iris (Iris douglasiana
Oregon grape (Mahonia repens)
California barberry (Mahonia pinnata)
Pink flowering currant (Ribes sanguineum
Golden currant (Ribes Aureum
Fuchsia-flowered gooseberry (Ribes Speciosum)

A regular contributor to Edible East Bay, Joshua Burman Thayer is a Bay Area permaculture designer and educator.

Photos: Joshua Burman Thayer

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