Published on 04/11/00

Unsteady Water Supply Bad For Plant Growth

Lack of water and water at the wrong time stress gardens and gardeners alike.

"Everyone knows what stress is, but very few seem to do anything about it," said Wayne McLaurin, a University of Georgia extension horticulturist. "Even in a perfect environment, stress can affect plants, and they can succumb and die."

For the past several years, unsteady water supplies have caused stress in backyard gardens.

Plants Like Steady Growth

"Plants don't like to grow in spurts," McLaurin said. "Hollies, for instance, would much prefer a nice, steady growth pattern rather than jumps, stops and starts throughout the year."

Water makes up 70 to 80 percent of holly plants and 98.5 percent of lettuce. Irish potatoes are 75-percent water. Lower the water supply, and all other growth elements tend to go awry.

Unlike landscape plants, there are no vegetables that don't require ample water. "Vegetables are shallow-rooted and just don't withstand drought," McLaurin said.

"All plant processes -- fertility use, movement of growth materials and plant-structure success -- depend on water," he said. "The reason plants wilt is that the reduction of water in the cells causes the cell walls to collapse.

"Nothing happens in the plant until water needs are met. All nutrients are dissolved in water. All uptake comes through water. All movement of materials in the plant is carried out by water. And in our hot, Southern summers, water is a key cooling agent of the plant."

Watering Tips

When it's not raining, what can you do to keep enough water on your plants? McLaurin offers these tips:

1. Water at the proper time. Don't wait until plants wilt and then give them a drink. Water early in the day so the plant won't get into stress.

2. How much water a plant needs depends on the plant type, the stage of growth and other factors. But generally, 1 inch of water per week will support most plants.

3. How to water is the critical point. The worst thing a gardener can do is to go home in the afternoon after work, see wilted plants, get the hose and spray them lightly.

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Photo: Wayne McLaurin

The most efficient way to water is at the root.
This generates two problems.

"You have just wet the top 1/32-inch of the soil," McLaurin said. "The feeder-root system didn't get any water that will sustain it over time."

Wetting the foliage also automatically sets up a potential disease problem. "The drier you keep the foliage," he said, "the lower the chance of disease. It's best if plants get that 1 inch of water in a way that gets it down into the root zone," McLaurin said.

For proper watering, apply an inch all at one time. To prevent overwatering, get a rain gauge and pick a day to check it. Make up the difference between the rainfall and the inch of water needed.

"The best way to water is drip or trickle irrigation," McLaurin said. "The average lawn sprinkler uses 300 gallons per hour. Drip uses low pressure and puts the water at the root zone where it will do the most good for the plant."

Drip irrigation uses about one-third of the water a sprinkler uses. "Gardeners can also mow or weed and never have to run from the sprinkler," McLaurin said.

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Photo: Tony Tyson

Drip irrigation is relatively easy to install in the landscape. Just run tubing where you need it, snap emitters into the tubing, and cover it with mulch.
"Another plus," he said, "is that drip irrigation is so easy to put together. Really, anyone can do it."

Most drip systems come with easy-to-follow directions. Check with your garden center for the systems that will work best for your needs.

Soaker hoses are another irrigation option. They use a lot more water than drip irrigation systems, but still much less than sprinklers.

Faith Peppers is the director of public affairs with the University of Georgia College of Agricultural and Environmental Sciences.