UNIVERSITY PARK, Pa. -- Established gardens or landscape sites usually do not feature many drought-tolerant plants. However, a horticulture specialist in Penn State's College of Agricultural Sciences says gardeners can take steps to keep gardens from drying up.

"A variety of techniques can be used to conserve water during times of moisture stress," says Bob Nuss, professor of ornamental horticulture. "Gardeners don't have to use all of them, but every little bit helps."

Mulches

Mulch is very effective at keeping moisture in the soil. Benefits during a drought include weed control, maintaining even soil temperatures, erosion control and improving the appearance of the garden. A 2- to 4-inch mulch layer is most effective.

"Whatever material you use depends on where it will be used, appearance and cost," Nuss says. "Homeowners can use two types of mulch: organic or inorganic. Make sure no mulch touches the plant stem or trunk."

Organic mulches range from shredded newspaper to shredded wood or wood chips. Inorganic mulches such as black plastic will be just as effective, although appearance may be an issue. "You can top-dress plastic mulches with gravel or wood chips," Nuss suggests. "But don't use gravel alone because it takes a layer 6 to 8 inches deep to slow moisture loss and control weeds."

Anti-desiccants

Moisture loss from plant leaves can be lessened or prevented by applying an anti-desiccant, which leaves a water-tight film over leaf surfaces.

"Anti-desiccants are most effective on evergreens and mature plants," Nuss says. "The film will not stretch when a new leaf grows, so gardeners must repeat the treatment as the plant grows."

Anti-desiccants can be applied to plants as a spray when air temperatures are above freezing, he says. "Anti-desiccants are invisible and easy to apply to small plants," he adds.

Wind screens

Plants can lose considerable amounts of moisture to active breezes. Plants maintain a constant layer of moisture vapor near the leaf surface, Nuss explains. If the moisture layer remains, it will slow the movement of more water from the leaf. When winds remove the moisture layer, plants must replace the layer with more water vapor from inside the leaf.

Nuss recommends using wind screens or barriers to slow air movement around plants. "Snow fence can be used bare or covered with burlap or plastic sheeting to block air flow," Nuss says. "Don't place the barriers too close to plants. They can trap heat against the plants, which increases moisture loss."

Most windbreaks will modify air movement for a distance of two times their height. For example, a 6-foot screen reduces the air flow for about 12 to 15 feet beyond the screen.

Nuss says gardeners can create a natural windscreen by planting a shrub border of drought-tolerant plants such as Mentor Barberry, Siberian Pea Shrub, Flowering Quince, Gray Dogwood, privet and bayberry.

Supplemental water

Nuss says much of the wastewater generated by a household can be used on plants -- with limitations. Water from bathing and clothes washers -- called "gray water" -- can be used on an ornamental garden if soaps and detergents have been diluted enough for irrigation. "Don't use water with chlorine bleach or boron," Nuss says. "Sodium from the salt used to soften water and liquid fabric softeners also can be harmful to plants."

Nuss says health experts advise not to use gray water on vegetables when there is a possibility of the water touching the edible portion of the plant. Watering the soil around fruiting plants such as tomato, pepper, bean and broccoli can be effective.

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EDITORS: For more information, contact Bob Nuss at 814-863-2196.

Contacts: John Wall jtw3@psu.edu 814-863-2719 814-865-1068 fax