For Release On Or After 04/29/11

By Dan Gill
LSU AgCenter Horticulturist

An important part of gardening successfully is learning to water your plants properly. Learning how to water properly is not complicated, but during hot, dry weather it can make a world of difference to the health of the plants in your landscape. New trees, shrubs and many warm-season bedding plants are planted in March, April and May. With intense heat right around the corner, watering will become increasingly important.

Most plants in the landscape, but particularly those planted this spring, may need supplemental watering during hot, dry weather conditions. Moisture stress due to lack of available water can result in reduced flowering, leaf drop, increased pest problems, substantial decline or even plant death and the loss of the investment they represent.

Gardeners use a variety of methods to water their plants, including hand watering with a hose or watering can, sprinklers of various types, soaker hoses and, occasionally, drip irrigation systems. Applying water deeply and thoroughly when needed is the key to proper watering.

Generally, trees, shrubs, lawns and ground covers that are well established in the landscape will need to be irrigated thoroughly once a week during extended hot, dry periods. Those planted this year, along with bedding plants and vegetables, may need to be watered thoroughly two to three times each week to do well under the same conditions.

Hand watering is ideal for watering plants growing in containers and hanging baskets. To water properly, apply water until you see it come out of the drainage holes. Plants in containers have a limited amount of soil for the roots to grow in, and they dry out very rapidly during hot, dry weather. These plants often need to be watered every day, especially those growing in smaller pots.

Don’t allow container plants to wilt before watering them. Even though they may revive, wilting causes damage that can lead to bud drop, leaf drop and scorched leaf edges. If you find that you need to water container plants more than once a day to prevent wilting, the plants are probably root bound and need to be repotted into a larger container, or you need to move them into a shadier location.

It is wonderfully relaxing to change into comfortable clothes at the end of the day, go outside and with your thumb over the end of the hose water plants in the landscape. But this shallow watering does not provide enough water to the plants, so it must be repeated frequently – often daily. This practice also encourages plants to produce more of their root systems close to the soil surface, increasing their susceptibility to drought stress. In other words, hand watering landscape plants may do more good for you than for the plants.

To properly irrigate lawns and plants growing in the ground, the water should penetrate at least 6 to 8 inches into the soil. Most of us don’t have the time or patience to apply water by hand slowly enough over sufficient time for it to penetrate that deeply, but sprinklers and soaker hoses will.

Sprinklers should be left on long enough to apply about one inch of water to the area being watered. One inch of water generally will penetrate about 6 inches into the average soil. To determine the time it takes for your sprinkler to apply one inch of water, place several straight-sided containers (such as cans) in the area to be watered, turn on your sprinkler and check the time. When the containers have accumulated an inch of water in them, check the time again. That’s how long it takes your sprinkler to apply adequate water. Apply an inch of water once a week to established plants whenever you don’t get a rainfall of at least one half to 1 inch.

Soaker hoses are good for beds and should be laid close to the base of the plants to be watered. They apply water very slowly and may require several hours to provide a thorough watering. The first time you use one, check how deeply moisture has penetrated by digging down with a trowel periodically to decide how long to leave the water running.

Newly planted individual trees are often best watered by laying the end of a hose near their base and turning on the water to a trickle. Leave the hose in place for about 20 to 30 minutes to saturate the root zone. Or you can fill a tree-irrigation bag, such as a Treegator. This should be done once a week during average, dry-weather conditions and two or three times a week during extended hot, dry periods.

You cannot directly damage your plants by watering them at the “wrong” time. The best time to water your plants, however, is during the early morning. That way your plants are well-supplied with water going into the hot afternoon. By watering early in the morning when it is cooler, less irrigation water is lost to evaporation. In addition, plants susceptible to fungus diseases, such as roses and lawns, are best watered when the foliage has a chance to dry rapidly. It will not burn your plants to water while the sun is shining on them.

It is possible to over-water plants, and over-watering can be just as bad as or worse than under-watering. Other than container plants, if you water properly you will not need to – and should not – water every day.

Proper watering is not that hard. But it is very important, especially when the weather is hot and dry. It basically requires watching the weather, paying attention to your plants, checking the moisture in the soil and common sense.