Central San Joaquin Valley gardeners often seem to be a little wary about designing and planting shade gardens. Maybe they’re thinking that the weather’s too hot for too long for shade plants to survive. That’s an incorrect assumption. Many shade plants do quite well here and can really brighten up dark spots in our gardens if we take steps to deal with several common problems.
Most shade plants need rich, well-draining acidic soil and few locations in our area have the ideal soil type. We need to amend the soil in shady planting beds with large amounts of humus or compost before we plant. We also need to lower our high soil pH levels from 7-plus (alkaline) to 6 or lower (acidic) by adding sulfur granules at planting time and twice a year thereafter.
Acid-type planting mixes can be added to the native soil as well as compost; just avoid using a planting mix that contains peat which dries out rock hard when irrigation is not sufficient. Established shade plants (camellias, azaleas, hydrangeas, most ferns) can be fairly drought- and heat-tolerant when planted in well-amended soil and when a 3- to 4-inch layer of mulch is maintained.
The first spots in the garden that many gardeners choose for planting shade plants is directly underneath the canopy of large trees where grass just won’t grow. There’s a reason why no grass, even shade grasses, grows under the canopies; the tree roots suck up all the water and nutrients. The roots do the same with other plantings which rarely thrive under the canopies. The extra irrigation needed to keep the shade plants growing under a tree canopy can harm the tree itself, especially drought-tolerant species such as Valley oaks. Better to lay down mulch under your Southern magnolias and find another shady spot for your heucheras (coral bells), gardenias and hostas.
The northern side of the garden will get the most shade, although even the northern planting beds may get some direct hot sun in July when the sun is at its most northern angle in the sky. The eastern side will get fewer hours of sun than the western side and the southern side will get the most – depending, of course, on the amount of shade cast by trees and structures.
Labels on shade plants will show “full shade,” “partial shade” and “partial sun.” You’ll want to count sun hours in the various spots in your shade garden to determine the best location for the plants’ needs. Full shade means less than three hours of sun; partial shade means three to six hours of sun with protection from midday sun; and partial sun means three to six hours of sun.
Also check labels for planting zone information. We’re in zones 8 and 9 in the Valley and zone 7 in the foothills.
If you haven’t checked the non-flowering shade plant displays at local nurseries and garden centers, you might be surprised to see the tremendous variety of foliage colors, shapes and textures available that can be added to the traditional flowering camellias, azaleas, gardenias and hydrangeas to create a spectacular shade garden.
Send Elinor Teague plant questions at firstname.lastname@example.org.