Recently, we had a client contact the Extension office asking about watering newly planted landscape shrubs. The client asked, “I have gotten such mixed messages on how I should have been watering — gardeners are telling me [water] every day; arborists and the nursery are saying [water] once a week, which I did. That didn’t work.” Both answers to the question of “how often to water” are technically incorrect if taken out of context.
The frequency of watering depends on your soil type, the weather, and the type of plant involved. Clay soils have a high water holding capacity and take longer to dry out compared to sandy soils. If you get an inch of rain per week in clay soils, you probably don’t need to water. If you get a half inch of rain in a week, you will need to supplement the equivalent of another half inch of rain a few days after the last rain event, if there is no rain in the forecast.
If you live in Florida with sandy soil and there’s a drought, you might have to water every day. Many of our former Florida residents that have migrated north tend to overwater their landscape plants because they don’t realize the difference in soil and climate. These are the neighbors whose advice on gardening should be taken with a grain of salt (or sand).
Another important factor is the time of year. Soil moisture evaporates more slowly during the cooler months of the year and you should water less often in the spring and fall compared to the summertime. During the winter months, you probably don’t need to water much, if any. If you’re in the middle of a summer drought and 100F degree temperatures, you might need to water every two or three days with newly planted trees and shrubs.
If the tree or shrub has been established for several years, you may not need to water unless in an extreme drought situation. Therefore, as the plant becomes more established over the first few years, you can gradually decrease watering frequency as the root system expands and is able to find water deeper in the soil. Ultimately, the best advice is “less is better” when it comes to watering well-established plants.
Another important factor is competition for water between plants. If you have shrubs planted near large trees with extensive root competition, then those shrubs are going to need more supplemental water than a shrub that has no competition. All these factors must be carefully balanced to decide when to water.
The type of plant is another important factor as far as tolerance to heat and drought. Plants with thin leaves, such as Hydrangeas, are going lose water and wilt more quickly compared to a plant that has thick, waxy leaves, such as a Camellia. New leaves in the springtime lose water at a faster rate (evapotranspiration) when the leaves are young and tender. As the leaves mature, they develop a thicker, waxy coating that slows down moisture loss, which normally occurs in summer.
Wilted leaves in the middle of the afternoon are deceiving and you can’t always go by appearances to determine if a plant truly needs water. Observing plant leaves in the morning is the best time to determine if they are truly wilted and whether the plant needs supplemental water. Plant roots must have oxygen for respiration and proper function—in fact, it’s good to let the soil dry out for a few days between watering. If roots become anaerobic in saturated soils, they begin to rot and the added stress to the roots makes them far more susceptible to fungal disease.
Proper planting technique and timing can reduce the time it takes for plant roots to become established and reduce stress associated with transplant shock. This is why the BEST time to plant new trees and shrubs is in the late fall or early winter months, which is the least stressful for the plant (and for the person digging the hole). Even though a plant is dormant, its roots are still growing throughout the winter and will establish more quickly since the plant is not losing water through it’s leaves. By the time summer begins, the plant’s roots will be in a better position to handle the heat.
For more information, see our free UGA Extension Bulletin 932, “Soil Preparation and Planting Procedures for Ornamental Plants in the Landscape” and Bulletin 1065, “Care of Ornamental Plants in the Landscape.”
Paul Pugliese is the Extension Coordinator and Agricultural & Natural Resources Agent for Bartow County Cooperative Extension, a partnership of The University of Georgia, The U.S. Department of Agriculture, and Bartow County. For more information and free farm, lawn, or garden publications, call (770) 387-5142 or visit our local website at extension.uga.edu/bartow.
