A Word to the Water-Wise: Start Tilling

Pocomoke crape myrtle, above, and salvia argentea (silver sage) are among the arid plants in the water-wise garden at Green Spring Gardens.
Pocomoke crape myrtle, above, and salvia argentea (silver sage) are among the arid plants in the water-wise garden at Green Spring Gardens. (Andrea Bruce Woodall - The Washington Post)
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Thursday, March 27, 2008

As the rest of us were doing watering triage last year and racking up huge utility bills, Audrey Faden gave two deep soakings to her drought-tolerant, or water-wise, demonstration garden in Alexandria and called it a day. The perennials, herbs, bulbs and shrubs performed adequately, survived without missing a beat and now look raring to go.

An early-flowering tulip, with short stems but stout blooms of yellow and rose, is this week in full glory in the garden, located at the parking lot entrance between the YMCA and Simpson Park in the city's Del Ray neighborhood. The tulips, of a variety named the First, have multiplied in the crest of the mounded garden, recalling the origins of the bulb in the hot, free-draining mountains of the Middle East.

Seven miles west, another demonstration plot, at Green Spring Gardens, also looked attractive last summer. The gardeners gave up on ailing annuals and delayed the fall vegetable garden, but the water-wise garden "looked beautiful," said Cindy Brown, Green Spring's assistant director.

As with all gardens of dry-tolerant plants, both these spaces began with a lot of soil amendments: You cannot prepare for the next drought, or generally reduce the use of water, by putting arid plants in regular garden beds and expecting them to survive or even flourish. Heavy clay and organic mulches are deadly to dry-loving plants, which have evolved mechanisms for dealing with heat and drought but rot easily.

So if you are serious about planting a drought-tolerant garden, have fun assembling plant lists and shopping for the chosen flora, but be prepared to do the ground work first. The beauty of a water-wise garden is that you can carve out a small area to try it and expand it later. The sunnier the site, the greater the choice of dry-loving plants.

Don't remove your clay soil, just build on top of it. Brown suggests raising beds by at least 12 inches. At Green Spring, the gardeners mixed compost with grit and rough sand.

The garden tended by Faden used excavated pond silt mixed with organic matter. The southern half is also amended with an expanded shale product called Solite. She also used a few large stones hidden in the berm and tilted inward to direct rainwater to the center.

Many water-wise gardens have a top layer of a few inches of pure gravel or grit, and Faden is planning to use various-sized gravel when she renovates the garden later this year. She tends it with her husband, Robert, and volunteers with the Master Gardeners of Northern Virginia.

Dry-loving plants tend to develop deep, far-reaching roots, which after a season or two reach down below a top layer of the aggregate to tap into the soil.

Some of the displayed plants are hard to find, such as a shrub called the leadplant, but many are commonly available, including lavenders, thyme, prickly pear, coreopsis and catmint. As a rule, Mediterranean herbs like it dry, as do most silver- and gray-leafed plants.

Various spurges are other good choices, including one whose lax stems pick up the maroon color of the lower leaf whorls. This species, called myrtle euphorbia, has clusters of acid-green blooms that have just opened. Stonecrops, a group of succulent plants that are all the rage in roof gardens, make great water-wise groundcovers as well. A species called Sedum sexangulare edges one side of the garden and still displays its attractive winter purple coloration.

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