Late summer color can be an opportunity to add new plant that will bring beauty to your garden right through fall. Many summer annuals are leggy and in need of cutting back about now. If you like spending time outdoors at this time of year take advantage of this glorious weather and make sure your garden has lots of colorful flowers.
Golden yellow perennials like gloriosa daisies, coreopsis and golden mums stand up to strong sun now, and later in the season burn like embers under gray skies. You’re probably familiar with the traditional Black-eyed Susan with a prominent purplish black cone in the center. There are many varieties of this type with russet, bronze or mahogany bands. But a gloriosa daisy I especially like has huge 5" golden yellow blooms with pale yellow tips and sports a light green central cone instead of the familiar brown one. Prairie Sun looks stunning with any shade of blue or lavender like asters, Russian sage or salvias. Try it in front of the sky blue flowers of cape plumbago for a breathtaking combination.
Gloriosa daisies make good cut flowers and are tough and easy to grow. They are descended from wild plants native to the eastern US and require only moderate water once established.
We are all interested in unthirsty plants these days. When I design gardens under our native oaks there are several principles that I follow that I want to share with you. Drought tolerant plants are a must in this situation. Evergreen oaks even have special needs requiring a different plant palette than deciduous oaks like blue and valley oaks.
Most oak roots are in the upper 3 ft of the soil. The roots which take up water and nutrients are in the upper 12". The critical root disease zone for an oak is within 6-10 ft of the trunk. Do not irrigate plants or disturb the soil in this area. Outside this zone but within the drip line one deep watering per month is allowable for your plantings.
The leaf mulch that accumulates under a large coast live oak increases soil moisture and available nutrients, improves soil structure and moderates soil temperature. It’s a valuable resource that can be used in other parts of the garden. Never remove the entire insulating layer of leaves from under a trees canopy and don’t allow leaf mulch to cover the trunk.
One of the showiest California natives for planting under a coast live oak is carpenteria californica or Bush anemone. This evergreen shrub is resistant to oak root fungus and grows in sun or shade. Although this plant can get by with no summer water after becoming established, occasional summer water will help maintain a fresher look. The compact variety ‘Elizabeth’ produces a profuse display of white flowers with as many as 20 flowers per cluster. Cut back the top 1/3 to 1/2 of the stems after flowering to keep it compact.
Another deer resistant plant I like to use under oaks is Centennial ceanothus. This gopher resistant low spreading groundcover grows 12" high and 8 ft wide. Cobalt blue flower clusters cover the plant each spring. They also attract birds.
Western redbud can be grown as an accent shrub or small tree under coast live oaks. Large bluish grey rounded leaves have heart-shaped base making quite a show among smaller leafed plants. The magenta sweet-pea shaped flowers cover the branches in spring. Scattered flowers may also appear in late summer and fall. Flattened seedpods rustle in the wind in late summer and fall. And if that’s not enough to love about western redbuds they brighten the landscape with a fall color display of yellow or red leaves. Western redbuds respond well to pruning. Thin the oldest trunks each year to keep them growing vigorously. You can also cut the entire clump to the ground to rejuvenate it. This is truly a four season plant.
Combine any of these plants with coffeeberry, native irises, pink-flowering currant, toyon, berberis aquifolium, snowberry, hummingbird sage or yerba buena to complete your woodland garden and keep your oaks happy too.
Visited a site yesterday under dozens of huge native oaks. The clients wants to plant a little landscaping here and there to enhance her property but not endanger her oaks. Naturally both deer and gophers abound. The deer trail goes right below her deck. I was able to give her some information about planting near oaks and will develop a plan for her installer to follow. There are several plants like mahonia ( now berberis ) that would require little water after becoming established and also I am considering ceanothus ‘Centennial’ for an area below the flagstone landing. I’ll add more to this post as I develop the planting plan for this beautiful property.
I’m designing an open space for a HOA for their housing tract. I’m planning on a central sitting area connected by a series of paths and surrounded by large flat Sonoma fieldstone rocks for sitting. This will be a challenging project as the plants used will not only have to be drought tolerant but will receive no irrigation at all after they are established. The site is browsed by deer so the plants will also need to be deer resistant and gopher resistant. . I think the concept I’ve developed will work and be useful for the residents.