Table of contents for Shaded Gardens
One of the challenges of turning a shady spot into a lush, colorful garden is to compose a mixture of plants that will grow together happily without root competition. After all, where sun is scarce, not only must plants vie for light, but there's usually competition for moisture and nutrients below ground.
The trick to having a care-free shade garden lies in matching plants to the site. Many plants, such as leafy hostas and colorful foxgloves and astilbes, thrive in filtered or partial shade. Their shallow or fleshy roots are adapted to share space with the roots of shade-loving neighbors. Here you'll find design and growing tips for getting a number of plants to thrive in filtered light.
The most successful approach to designing a care-free garden in filtered or partial shade is to stagger the heights of bedfellows so that they are stacked in layers, according to their heights. This kind of layering exists along the edge of a natural woodland, where tall trees give way to smaller ones like dogwoods, then to shrubs like viburnums and azaleas, and finally to perennials, annuals, and groundcovers. Besides being a highly hospitable situation for plants that are adapted to share light and root space, this design allows small, showy plants to be showcased against the backdrop of taller ones. This kind of layering also creates an ideal habitat for birds, drawing a greater number of species to your garden, because in nature, each species occupies a different layer, which limits competition for food and nesting places.
Filtered and Partial Shade
Filtered and partial shade are different ways of blocking sunlight, but the end result is that plants in each situation receive about the same amount of light. Filtered shade can be found beneath any open canopy that provides dappled sunlight throughout the day. The source of filtered shade might be the overhead boughs of a loose limbed or small-leaved tree, such as dogwood, silverbell, or stewartia, or perhaps very tall, widely spaced evergreen pines. Filtered shade is also found beneath a pergola, an arbor, or beside a picket fence or lattice panel. Plants grown in filtered shade often show a full, mounded shape and rarely stretch toward the sun, because they receive a steady, yet intermittent, light supply all day long.
The same plants that grow in filtered shade also often thrive in partial shade, a situation in which buildings, walls or thick tree canopies; or closely spaced trees and shrubs block light for all but 3 to 4 hours daily. The best kind of partial-shade situation for gardening is usually found on the east side of a house or along a woodland edge, where plants receive sunlight in the cooler hours of the morning and are shaded and protected from the hot afternoon sun. Morning sun dries dew from plant leaves promptly, which reduces fungal diseases, and it gives plants a short but intense period of exposure to sunlight, followed by a long recovery period in the afternoon. This is a situation that can help you grow a wider selection of plants than you normally could if you live in a hot-summer climate, because many plants that grow in full sun in cooler climates can wilt and eventually die if exposed to full sun in hot areas.
Turning a Concept Around
Don't give up on sites that are shaded in the morning and sunny in the afternoon. This is often an ideal niche for plants that are usually grown in full sun, yet can adapt to partial shade. Some of these include begonia, pansy, phormium. and summer-flowering bulbs, such as lily and gladioli, along with perennials like ornamental grasses, yucca, and sedum. In hot-summer climates you may have great success if you try growing perennials that prefer full sun in cooler summer conditions, such as catmint and veronica, by planting them in a spot where they receive full sun only in the afternoon.
The Underground Story
Underneath it all, thirsty tree roots are always competing with garden plants for water and nutrients. Trees with many surface roots, such as birches, beeches, maples, and apples, are the worst offenders. If you're planting beneath a shallow-rooted tree, consider planting dry-soil-adapted groundcovers like vinca or epimedium. Or build a shallow berm or raised bed. Keep the bed at least 6 feet from the trunk of the tree to prevent damage to the trunk and shallow roots. Line the floor of the bed with thick, perforated plastic to keep tree roots from invading your bed. To avoid root competition altogether, create shade gardens under tree species with deeper roots, such as oak, hickory, or other nut trees.