Daniel Gill, Merrill, Thomas A. | 4/4/2006 11:45:44 PM
By Dan Gill
LSU AgCenter Horticulturist
An important part of successfully gardening is learning to water your plants properly. Doing it correctly is not complicated, but during hot, dry weather watering appropriately can make a world of difference to the health of the plants in your landscape.
New trees, shrubs and lots of warm-season bedding plants are planted around here in March, April and May. With intense heat right around the corner, watering those plants properly will become increasingly important.
All plants in the landscape, but particularly those planted this spring, may need supplemental watering during hot, dry weather. Moisture stress from lack of available water can result in reduced flowering, leaf drop, increased pest problems, substantial decline or even death of plants 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 will need to be irrigated thoroughly once a week during extended hot, dry periods. Those planted this year, along with bedding plants and vegetables, however, 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 dry out very rapidly during hot, dry weather. They often need to be watered every day, especially those growing in smaller pots.
Do not 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 probably are 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, take the water hose, put your thumb over the end of it and water plants in the landscape that way. But this shallow watering does not provide enough water to the plants, so it must be repeated frequently (often daily). It also encourages plants to produce more of their root system close to the soil surface – increasing their susceptibility to drought stress. In other words, hand watering may do you more good than it does the plants.
To properly water lawns and plants growing in the ground, the water should penetrate at least 6 inches to 8 inches into the soil. Most of us do not 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 an inch of water to the area being watered. That inch of water applied to the surface should penetrate about 6 inches into the average soil. To determine the time it takes for your sprinkler to apply 1 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. The difference between the start time and the time you find an inch of water in the cans is how long it takes your sprinkler to apply adequate water. Apply an inch of water once a week to established plants until a rainfall of at least a half inch to an inch occurs.
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 it on.
Newly planted individual trees often are best watered by laying the end of a hose near their base and turning the water on trickle. Leave in place for about 20 minutes to 30 minutes to saturate their root zones. This should be done once a week during average 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. In addition, by watering early in the morning when it is cooler, less irrigation water is lost to evaporation.
Watering in the morning also is best for plants that are susceptible to fungus diseases, such as roses and lawns, since it gives the foliage a better chance to dry rapidly. Despite what some people say, it will not burn your plants to water while the sun is shining on them.
It is possible to over-water plants, however, and over-watering can be just as bad or worse than under-watering. For everything but container plants, which can be watered more often, 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 simply requires watching the weather, paying attention to your plants and common sense.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.