Daniel Gill, Merrill, Thomas A.
During the summer, dry conditions and high temperatures may make it necessary to irrigate established trees, shrubs, lawns and flower and vegetable gardens.
Even more critical is the need to regularly and properly water new plantings and plants growing in containers. These plants are particularly dependent on the gardener for water when the weather is dry.
Proper watering can make the difference between life and death to recently planted lawns, ground covers, trees and shrubs. Because their roots have not had time to grow out into the soil, these plants do not yet have well- established root systems. With their root systems still limited to a relatively small area of soil, they are especially vulnerable to drought stress.
The first summer after planting is the most critical time for newly planted trees, and proper watering plays a major role in whether or not they survive. Here are two ways to properly provide water to newly planted trees during hot, dry weather.
For the first method, turn a hose on trickle, lay the end on top of the ground within 6 inches of the tree’s trunk and let the water trickle for about 30 minutes.
Or, build a 4-inch levee out of soil around the edge of the area dug up to plant the tree. Fill this area with water and let it slowly seep into the root zone.
Use either of these techniques during hot, dry weather – whenever seven to 10 days pass without substantial rainfall – and continue to water once or twice a week until a good rain occurs (one-half inch or more). Drought-stressed trees may experience wilting, leaf drop, yellow or brown leaves, scorched leaf edges or even death.
Generally, newly planted beds of shrubs may be watered with soaker hoses or sprinklers, just as you would established shrubs. They will, however, need to be monitored more carefully and watered more frequently.
Situations can arise where newly planted shrubs are damaged or killed by drought stress despite your best efforts. Remember, all of a newly planted shrub’s roots are in a small area – about the size of the pot the shrub was growing in before planting. This is especially true for shrubs planted after March, since they have had little time to grow roots into the surrounding soil.
A shrub can use up all the water in its root ball and become drought stressed even though the soil in the bed outside of the root ball is moist. In this situation, it is best to water each shrub individually, as needed, with a hose trickling water as described for trees (leave the hose by each shrub for about 10 minutes).
Watch new shrub plantings carefully for the same drought symptoms described for trees. Summer-flowering shrubs, such as hibiscus and crape myrtle, may abort and drop their flower buds if drought stressed.
Summer is a great time to lay sod to install a new lawn or repair an established one. But newly laid sod needs special attention to watering.
Apply one-quarter to one-half inch of water every day for the first seven to 10 days after the sod is laid. Then apply one-half inch of water every other day for another seven to 10 days. Continue to irrigate the lawn with an inch of water once or a week, as needed, to encourage the roots to grow deep into the soil. Do not water every day for more than 10 days or you may encourage fungus diseases.
Watering plants in containers outside is a constant job during the summer. It is typical to water every day or even twice a day when weather is hot and dry. Certainly keep this in mind when considering how many outside container plants you can maintain.
How often you have to water is influenced by temperature, pot size, the type of potting soil, the drought tolerance of a plant, whether a plant is in sun or shade and how pot-bound a plant is. Plants need to be watered more frequently when it is hot, when the containers are small, when a light soilless potting mix is used, when plants are in a sunny location and when plants are pot-bound. Clay pots also tend to dry out faster that plastic or glazed ceramic pots.
To reduce how often you have to water outside container plants, use larger rather than smaller pots, choose a potting mix that retains more water (it must still be fast draining), repot pot-bound plants into larger containers, use plastic or glazed ceramic pots and, if practical, move the plants into somewhat shadier conditions.
Some gardeners have successfully rigged drip irrigation systems, available at nurseries and building supply stores, to water their container plant collections. Set them to come on with automatic timers, and these systems can greatly reduce the effort of keeping container plants watered. Self-watering pots that include a built-in water reservoir also might work in some situations.
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.