Gardening in the shade presents special challenges for homes in wooded areas, yard areas with many trees, landscape beds on the north side of houses or areas near decks and other structures that cast heavy shade.
Shade can be defined in varying degrees, such as light shade (3-4 hours shade each day) to full shade with no direct sunlight and only indirect light. Heavy shade would include sites under evergreens and decks and trees shading the north side of the house, with minimal indirect light. The degree of shade can change depending on the season and sun position, and the species casting the shade. This should be considered in the landscape. For example, after an early bulb such as spring crocus blooms, the leaves need light to grow and develop next year's flowers. If it is planted under a late-leafing tree such as oak, this requirement can be met, but under a maple that casts earlier shade, the bulb may not bloom well from year to year.
The greatest challenge of shade gardening is selecting plants that will not only grow, but thrive under various low-light regimes. Additional challenges include proper fertilization, often dry but sometimes too wet soil conditions, lack of air movement that encourages diseases, and problems with slugs, snails and other pests that thrive under cool, moist conditions. Moss will also form under moist, shady conditions, and can be unsightly if it becomes excessive.
Plants that that thrive under less than ideal light conditions are of many types and include species of trees, shrubs, perennials and annuals. Many plants well-known for their shade tolerance such as hostas or redbud trees are easy to find at garden centers. Other species may not be easily found and a search of catalogs or online nurseries may be needed to locate particular plants known for shade tolerance. Often we may be surprised at how plants known to do best in sunny conditions can adjust to light or moderate shade in which some direct sunlight occurs. Though they may not bloom as fully or have as brilliant fall color when in full sun, they still perform satisfactorily in the landscape.
Plants growing under shade conditions respond well to compost and organic matter additions and loosening of the soil prior to planting. This is because shaded areas are typically dry due to tree and other plant root competition for water, and many shade tolerant plants tend to have shallow root systems. Care should always be taken to minimize injury to existing plant roots when preparing new areas for planting.
Plants growing under shade should be regularly watered (~1 inch/week depending on rainfall), kept cool and damp but not overly saturated, which will encourage diseases. When possible spot or directed watering is a better approach than sprinkling large areas. This conserves water and gets it to the roots of desirable plants and not to neighboring large trees which do not require weekly watering. Watering should also be done in the morning so that leaves have time to dry during the day. Often, most shade tolerant plants, especially perennials and annuals, have large leaves which capture more light. However, even considering leafy growth, fertilizer additions should be moderated and one-third to one-half of what plants growing in the full sun would require. Therefore, when using soluble materials such as Miracle Gro™, choose a lower nitrogen formulation (less than 10% N) or mix a higher formulation at less than the normal rate. Fertilizer should also be applied more infrequently in shady areas (every 6-8 week) compared to beds in full sun conditions.
Mulching will also help conserve moisture under more competitive shade conditions, and lessen weed growth. Beds should also be kept weed free to reduce competition for water, nutrients and light.
The following is a partial list of plants known to have light to moderate shade tolerance:
Trees:
Redbud, White Fringetree, Carolina Silverbell, Witch Hazel, Black Gum, Flowering Dogwood, Kousa Dogwood, Japanese, Amur, Sugar and Paperbark Maples, Katsura Tree, American Hornbeam, Cockspur Hawthorn, Serviceberry and Red Buckeye.
Deciduous Shrubs:
Fothergilla, Oakleaf and Tardiva Hydrangea, St. Johns Wort, Japanese Kerria, Bush Cinquefoil, Black Chokeberry, Red and Yellow Twig Dogwood, Japanese Barberry, Enkianthus, Dwarf Burning Bush, Doublefile, Arrowwood and Cranberry Bush Viburnams, Privet, Rose of Sharon, Spicebush
Evergreens (trees and shrubs):
Hemlock, Yew, Oregon Grape Holly, Catawba Rhododendron and Azaleas, Japanese Pieris, Boxwood, Leucothoe, Mountain Laurel
For a more extensive listing of shade tolerant plants, visit these University of Illinois Extension websites which list plants by exposure preference and other cultural criteria:
