Published on 06/03/96

Help Garden, Landscape Through Dry Times

Gardens, lawns, trees and shrubs feel the burn of inevitable dry times in broiling Georgia summers.

But you can slake your plants' thirst until the rains come, says Wayne McLaurin, a horticulturist with the University of Georgia Extension Service.

Plants need soil moisture to grow. In fact, a healthy plant is 75 percent to 90 percent water. During this critical time in their growing season, plants just can't do without, McLaurin says.

"Vegetable crops need about an inch of water per week from rain, irrigation or both," he says. "Keep a rain gauge near the garden or check with the local weather bureau for rainfall amounts. Supplement rainfall with irrigation water if needed."

During dry times, a single thorough, weekly watering of one to two inches (65 to 130 gallons per 100 square feet) is enough for most soils. Wet soils five to six inches deep each time you water, and don't water again until the top few inches begin to dry out. The average garden soil will store two to four inches of water per foot of depth.

You can reduce the water you need by using some simple conservation techniques:

* Add organic matter. Soil moisture may not be available to plants, particularly if the soil is a heavy clay, which tends to retain water.

For example, if four and a half inches of water per foot are in a heavy clay soil, as little as one and a half inches may be available for plants. A fairly high level of humus in the soil can make more water available to plants.

Adding organic matter also improves the moisture-holding capacity of sandy soils. Although most water in sandy soil is available for plants, it drains so quickly that even a few days after rain, plants can't reach it. Humus in sandy soil gives the water something to cling to until the plants need it.

* Mulching can greatly reduce your watering needs. A three- to four-inch layer of organic mulch can cut water needs in half.

Mulch smothers weeds and keeps water from evaporating so fast from the soil. Organic mulches hold some water themselves and increase the humidity around a plant.

Black plastic mulch also conserves moisture. But it may make the soil dramatically hotter during summer if it isn'>t covered by other mulches.

* Shading and windbreaks can also help conserve moisture. Plants that wilt in very sunny areas can benefit from partial shade in the afternoon. Protect small plants.

When the rains don't come and the plants are suffering, it's time to irrigate.

"The home gardener has several options for watering plants," McLaurin says. "Use a sprinkler can, a garden hose with a fan nozzle or spray attachment, portable lawn sprinklers, a perforated plastic soaker hose, drip or trickle irrigation or a semiautomatic drip system."

Several types of drip or trickle equipment are available. The soaker hose is probably the least expensive and easiest to use. It's a fibrous hose that allows water to slowly seep out along its length.

Hoses perforated with tiny holes do the same thing: water slowly drips out of the holes.

An emitter-type system works best for small raised beds or container gardens. Short tubes, or emitters, extend from a main water supply hose and directly deposit water at the roots of selected plants.

This is generally the most expensive form of irrigation and the hardest to set up. But weeds don't get watered and you don't lose much water through evaporation.

Emitter systems are most effective when combined with coarse mulch or black plastic. Drip systems sometimes clog with soil particles or mineral salts from spring or well water. But some new designs include filters and self-flushing emitters.

"Plants don't waste water. People do," McLaurin says.