In Every Dimension, a Landscape of Possibilities

Using vertical elements to subdivide an area, whether they are structural such as fencing or natural such as groupings of trees and shrubs, can make the space appear larger while providing a sense of privacy. (Photos By Sandra Leavitt Lerner For The Washington Post)

Landscape design is a three-dimensional discipline. You control the depth, breadth and ceiling of your space, and it can run as far as you allow the eye to travel.

Adding a path can expand your view, taking you through a hedge and under an arbor, then disappearing around a curve, giving the illusion that you might follow it for some distance. These sorts of effects are created by considering all levels of the garden, and the ground, vertical and overhead planes are equally important.

Ground

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This is where elements such as paving, lawns, low ground covers, perennials and annuals meet the soil. It's the foundation of the garden, and it dictates pedestrian and vehicular circulation. Paths and paved surfaces direct us to a destination.

Stability underfoot requires soil low in organic matter and high in mineral content with good weight-bearing ability.

Build structures on soil that has been undisturbed for several years so there is no chance of settling when you lay a walk or wall.

Nearly all plants begin on the ground plane. Most flora require loose, moist, well-drained soil high in organic material. Walking, hiking or riding over an area just once can affect what will grow there by compacting the soil.

Pollution from cars and industry, insects, disease, neglect, and droughts also affect plants on this plane, but plants can better deal with environmental extremes if their medium is properly prepared.

Lay three inches of compost over the soil surface, then till or spade it 10 to 12 inches into the soil. If your own compost isn't ready yet, buy some at the garden center under the name Leafgro or look for the availability of composted leaves through your jurisdiction.

The only way to know if you need fertilizer or lime to change the soil's acidity or alkalinity is by testing. Check with your local extension service. Some garden centers also offer soil testing and meters to check pH. All plants have different requirements. The "LaMotte Soil Handbook," available from the LaMotte Co. ( http://www.lamotte.com), lists the soil testing and pH needs of a variety of plants.

One crucial element on the ground plane is natural carpeting. Bare areas under plants can develop runoff problems, and steep banks can erode. Acres of lawns are planted for this purpose, but turf grass is not practical under shrubs or on steep slopes, so other types of cover should be used.

Beautiful, plush carpets are available that discourage weeds and control erosion. They come in green, gray-green, blue-green and red, with variegations of gold, white, cream, red and pink.

Here are a few possibilities for carpeting your garden: wild ginger ( Asarum canadense), creeping juniper ( Juniperus horizontalis), creeping phlox ( P. subulata), Japanese spurge ( Pachysandra terminalis), Allegheny spurge ( Pachysandra procumbens), wild stonecrop ( Sedum ternatum), periwinkle ( Vinca minor) and St. John's wort ( Hypericum calycinum). All are native ground covers except periwinkle and Japanese spurge.