Planting under oak trees in California

There are many plants that grow naturally under oaks in California. Some genera are common in most of California and are commonly associated with oaks. Plants that are not normally associated with oaks cause many problems for the oaks and the oaks and their allies will expend resources attempting to exclude them. Research has shown that this occurs, but the specific causes are harder to identify. We've seen many times, over many years, diseased trees with a near leafless canopy come back to health by controlling the weeds, lawn or petunias.

Ribes, the currants and gooseberries commonly grow in oak forests. On the north slopes the currants grow at the drip lines of the trees, gooseberries grow in the openings. On the south slopes the gooseberries grow up under the drip line of the trees. People wonder where the native birds went, Ribes provide flowers for nectar, nesting sites, thorns for protection,  and berries for food. Does your yard have those?

Rhamnus, coffeeberry and redberry. The Rhamnus genera grow in association with oaks. We've had a number of people that want to plant 'that little oak with red berries' (Rhamnus crocea or Rhamnus ilicifolia). They grow with the oaks and kinda look like an oak. The root systems are similar to oaks and commonly share resources with oaks. That is good.

Ceanothus, the California mountain lilacs usually do not grow in the deep shade of oaks, but love the edges, half day sun, or under deciduous oaks. Using Ceanothus or Arctostaphylos, you can leave the heavy mulch under the trees alone and plant the drip line(edge of tree canopy) to make the oak look landscaped. Ceanothus like Yankee Point and Joyce Coulter will tolerate near full shade where summers exceed 100 F (37C) regularly.

Solanum, nightshades. The nightshades are common under the oaks in most of the coastal regions of California. Great bird plant that has decent looking blue flowers in summer. Plant Vinca major for the rats, Solanum for the birds.

Yerba Buena, Satureja douglasii grows in the leaf litter of Coast Live oaks, Canyon Live oaks and even Blue Oaks. Excellent along serene walkways and under benches as it's flat and it smells real good.

Satureja chanderi, Mountain Balm is a shrubbier form (1  feet)  that grows under oaks in Southern California. A snoot will find this cute beaut is a hoot and smells mighty fine. Mountain Balm is huggy, not buggy,  and makes a very clean mass of green.

Elymus condensatus, Giant Rye is one of the few grasses that grows under oaks. Although Giant Rye will grow in full sun, particularly with regular water, it will grow well in full shade with no extra water in most of California. For those of you that seem to want a grassy prairie and don't know a buffalo from an, oh I guess I can't type that.

Diplacus , the shrubby monkey flowers love the edges and half day sun under oaks. Full shade is a bit too much for monkey flowers, but full sun is commonly too much. Those little spots of sun under the oaks where the hallo of sun beams come together in the afternoon is where you plant these. Put a garden bench near that spot with Yerba Buena under it and the monkey flowers/ hummingbird sage as the feast to look upon.

Saliva spathacea. Hummingbird sage grows great under the oaks. In the wild Hummingbird sage grows in full shade and into full sun. I've only seen a few spots where the weeds haven't overwhelmed the sage and stunted the tree. In one spot one plant had filled an area of 50X50 feet with the foliage just above the leaf litter making a carpet of green with pink/magenta flowers that the hummingbirds love.

The question is, is this thing really a sage?

Heuchera maxima and Heuchera micrantha.

The larger alum roots grow well under oak trees. They form a great interface between a wet spot and the trees. Full shade to part shade, Heuchera doesn't like full sun and tolerates the oaks very well.

Monardella villosa and some of the Coyote Mints grow under or at the edge of oak trees in much of California. Big hat perennial ladies, butterflies and hummingbirds like these. Nice flowers and they smell nice.

Lonicera hispidula and Lonicera denutata Let's see, honeysuckles are generally evergreen, have pretty flowers, need little care, are usually not eaten by deer, have berries for the birds and are decent to look at.

Toyon grows under oaks in most of California. Near the immediate coast Toyons move into the sun but in areas like Los Angeles or Riverside, Toyons are mixed with the oaks and commonly grow even at the trunks.

Rhus trilobata, Squaw Bush grows under oaks in the interior coastal valleys. A deciduous sub-shrub that has great fall color and berries for the birds. Funny, the people who HATE deciduous plants are often the ones looking for 'fall color'.

Lepechinia fragrans and Lepechinia calycina both do well under oaks with little care. Pitcher plants can grow in full shade into part sun. Picture a six foot high shrub with digitalis flowers.

Keckellia cordifolia grows great under coast live oaks, Keckellia breviflora grows great under the deciduous oaks , but has also done ok here under our coast live oaks. This is a deciduous penstemon, dead stickus in fall, pretty flowers in summer.

Interesting photo, pistil looks 3d, I thought it was a scratch on my monitor.

Amelanchier, the Service Berries can be very interesting as a contrast to the oaks. In many of the coastal woods Service berry can become a mini-tree under the high shade of oaks. Sometimes you'll have the full 100 foot oak, then the 10 foot service berry 'tree' and under it either Satureja douglasii or Symphoricarpus or Lonicera. Sometimes there's even a Ribes between the oak and the Amelanchier.

Symphoricarpos albus and Symphoricarpos mollis both are snowberries and both grow well under oaks. Thrashers, Thrushes, and other native birds use the berries as survival food in winter. The berries taste like Ivory soap, but I'm not a bird, maybe it tastes different to them.

Good things to do.

Plant associated plants.

Plant junk that has never grown near an oak tree and needs a ton of water and fertilizer. Why would you expect a plant that grows in full sun along a river in Brazil to grow under your oak? A lawn also comes to mind. If you did use a ton of water, gradually remove the input over a couple of years.

Leave the oak leaves.

Remove the leaves from under the oaks. Bare ground and green weeds are better than that nasty layer of leaves. THE OAK NEEDS THE LEAVES!

Think like a tree. Long term, no sudden changes, no tilling, disking, poop, or water Lean and mean. Hang a hammock and put yourself in it. .

Plant short term stuff and kill the tree slowly. Pansies and petunias are a cruel joke under an oak.

Prune out the dead stuff and trim the branches up off of the ground.

Prune the trees hard or in some weird manner like pollarding. Forcing new growth draws from the trees resources and often triggers a cascading failure in the system of the oak tree.

You can wash the foliage off occasionally on dry, dusty years.

Put a lawn under the tree and you'll have a sick lawn and a sick tree.