Consider proper area for plants

By Ed Perry

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A gardener who was considering planting a grapevine recently called to discuss the sunlight requirements for grapevines. It was a very important question to ask, especially before going ahead with the planting. All plants require some amount of sunlight, but some species need many hours of full sun while others do well largely in shade.

Before choosing plants for your garden and landscape, observe how many hours of sun and shade various parts of the site receive. Remember to take into account that the angle of the sun changes with the time of year and that you will probably have more hours of direct sun in summer than in other seasons.

For most fruit trees and vines, a full eight hours of sunlight is required for best growth and fruit production. Fruit trees will grow and bear fruit in partial shade, but they will take longer to begin bearing fruit, and fruit production and quality will be reduced as the amount of sunlight is reduced. Fruit trees and grapevines growing in shaded areas will also be more susceptible to certain diseases, such as powdery mildew. Remember that fruit trees areshaded by not only buildings, fences and taller shade trees, but by other fruit trees. When planting, be sure to allow adequate space between trees to prevent excessive shading when the trees grow to maturity. As is used in some commercial orchard plantings, you can use competition between fruit trees to reduce vigor and size, or to enhance flowering. However, this is accomplished through special planting, training and pruning "high density" arrangements rather than planting young trees directly into crowded and shaded conditions.

Landscape plants requiring full sun usually need at least six hours daily of direct sun, and often produce the best form and growth if they receive sun all day. Plants that can tolerate full sun to partial sun will need around three-four hours of direct sun. When young trees or shrubs that require full sun are planted under or near the canopy of established trees, they will bend in the direction of the sunlight and become deformed. Choose shade-tolerant plants for planting in the shade of established trees.

Trees and shrubs that tolerate shade will perform best in filtered or partial sun rather than full shade. Most shade tolerant trees are small, understory trees that grow naturally in woods openings or along forest edges. They are best suited to growing in partial or dappled shade, or in morning sun and afternoon shade. Some examples of trees that do well in filtered shade are Eastern redbud, flowering dogwood and Japanese maple. Most shrubs are also shade tolerant rather than shade loving, and will grow best in dappled or partial shade or in morning sun and afternoon shade. Some examples of evergreen shrubs that tolerate shade are acuba, azalea, camellia, fatsia, gardenia, heavenly bamboo, Japanese euonymus, Japanese pittosporum and laurustinus.

Shade-loving perennials and groundcovers are better suited for heavily shaded locations with less than two hours of morning sun. Examples of perennials include bear's breech, coral bells and Lenten rose. Examples of shade-loving groundcovers are bugleweed, pachysandra, vinca and ivy.

When selecting plants, remember that a number of factors determine the suitability of a plant. Along with adaptability to shade, also consider moisture availability, soil type, hardiness and heat tolerance.

Ed Perry, a farm adviser with the UC Cooperative Extension, can be contacted at 525-6800 or ejperry@ucdavis.edu.