Rocks Can Help Create a Natural, Low-Maintenance Garden

You can be innovative in your use of specimens. I've seen the almost-Stonehenge-size six-footers staggered to provide partial screening and a dramatic effect. You can also plant stones in the soil as steps. Use big flat ones arranged in a comfortable fashion on a slope.

The issue with specimen rocks is that they weigh a ton -- really. Like other large, heavy objects, specimen rocks can be expensive to buy and expensive to transport and place. At least they never have to be replaced.

You will need some kind of equipment to move and place them. When I order rocks for a client's landscape, they're usually delivered in a truck that includes a self-contained crane and a highly experienced operator to lift and place them. Placement is extremely important, so the contractor you work with must be patient.

This effort and expense can limit the use of ornamental rocks in the landscape. However, nature has produced lava rock, and modern technology has stepped in with artificial rocks that look authentic.

Lava rock is a porous volcanic material, significantly lighter than other stone because it is full of air pockets. It's available in black, brown, russet or gray at stone suppliers and garden centers. These rocks don't fit the native garden theme, but they do work in other types of natural gardens, including Japanese.

Most synthetic rocks are composites of several materials, primarily colored fiberglass. A person could single-handedly lift a piece of artificial rock that would weigh six tons if it were real. Ersatz rocks are being used more often and are available from the companies that fabricate them.

Smaller rocks can be used in many ways. Low rock retaining walls are charming additions that give a manicured look to a rustic, natural garden. Wall-size flat rocks, up to a foot or so wide, can be organized and stacked without mortar to build a low wall.

Rock is the perfect enhancement for water features. Stone coping around a natural water feature such as a lily pond fits the rockscaping theme. Stones can also be used to create fountains, with water bubbling up out of or gently falling down them. Rocks can also be used to create waterfalls in a natural or artificial stream.

Gravel-type rocks can range from tiny pea sizes to four-inch or so "river" rocks. Aggregate mulch gives a southwestern feel to a garden. Mix it with sand, larger rocks and cacti. This is not a natural look for the mid-Atlantic area, but cacti, yuccas, agaves and other desert plants look good mulched with stone. Make sure the area is well drained.

Stone can be used to imply a riverbed and at the same time serve as an effective and ornamental drainage swale. Cover the soil surface of a U- or V-shaped, meandering depression with a consistent aggregate material such as rounded river gravel. Mix varying sized larger rocks for a natural stream design.

One beautifully ornamental use of small gravel is to create a formal Italian pebble garden, such as the one at Dumbarton Oaks in Georgetown. Different colored small stones are shaped into intricate designs that look formal and natural at the same time. Use colorful crushed or rounded gravel for a variety of appearances. Set the stones in mortar, or simply lay them in steel or aluminum frames. You can also separate them into geometric designs with wooden strips in between. Pebble designs look wonderful under running water, as from a fountain.

These materials are available at garden centers, stone yards and quarries. Check the phone book under "Stone-natural" or "Quarries" or use a search engine on the Internet to find manufacturers of artificial rocks.

This is the perfect time to design and place landscape stones. Plants are just breaking out of dormancy, so you can see the bones of the landscape. Early bulbs are just appearing, so you can arrange rocks around them.

Who knows? You might become so fond of your garden's Martian aspects that you give the rocks names, as NASA scientists are doing.

Next week: Rock gardens

Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. E-mail or contact him through his Web site, www.gardenlerner.com.