Matthew Orwat
County Extension Agent – AG/NR
Email: matthew.orwat@ag.tamu.edu
One of the most common questions we get is how much to water a tree. The answer, as with a lot of gardening questions, is it depends on environmental factors. Hot, windy days with low humidity mean your tree uses a lot more water than cool, still days that are humid.
Where to Water
You want to water the entire root zone of the tree. The root zone is larger than the canopy. When trees are first planted, make a berm about two-three feet in diameter around the new tree. The berm should be about 3 inches high. Older trees don’t a berm but need you to wet the ground to a depth of 12-18 inches deep all under the canopy and a few feet beyond it.
Tree watered with a soaker house in root zone. Image Credit Texas A&M Forest Service
How to Water
For new trees, fill up the area inside the berm and let the water soak in. Repeat this one time. For older trees, irrigate 1-3 inches of water over the entire canopy and about two feet further. You can figure out how much time it takes your sprinkler to put out that much water by putting small cans on the ground and timing how long it takes to put an inch of water in the can. Multiply that by the number of inches you are trying to disperse. Another way of thinking about the watering is 2-4 gallons of water under the canopy for each inch of tree trunk diameter chest high on the tree. Water the higher number in the summer and the lower number in the winter.
How Often to Water
The goal of watering your tree is to keep the soil moist down to 12-18 inches of soil depth. How often you have to water depends on the weather. A soil probe will help you see how deep the water goes.
Newly Planted Trees
Texas A&M Forest Service suggests this schedule for watering newly planted trees for the first two years after planting. The first month, water 3 times a week. The second month, water 2 times a week. The third month, water 1 time a week. For months 4-12, water once a month. After that, you need to water once a month if it doesn’t rain the second year.
Old Trees
Trees three years old and older get watered once a month if the soil is dry at a depth of 12-18 inches. Native trees usually do fine with the amount of rainfall they get unless there is a drought. You will need to water them once a month in that case.
Symptoms of Underwatering
The first sign of underwatering, or drought stress, is wilting leaves. In addition to leaf wilt, leaf folding or rolling, leaf scorch, leaf yellowing, premature leaf drop, or leaf death, and overall tree decline are all possible symptoms of underwatering. When drought stressed, a tree is more vulnerable to diseases and pests.
Symptoms of Overwatering
Oddly enough, the symptoms of overwatering are the same as those of underwatering. Soggy soil keeps air from circulating to the roots, damages the fine root hairs, and can cause root rot. The roots are then unable to absorb water, no matter how much water is around the tree. Lack of water is what kills the tree.
Mulch Around Your Trees
Mulching around your trees helps resist weeds, protect the tree from mower and string trimmer wounds, stabilizes soil temperature, and conserves soil moisture. Three inches of hardwood mulch should be placed in a ring around the tree. Leave a space of about three inches between the tree trunk and the mulch. Continue the mulch for at least three feet around the tree.
Mulch decomposes at a rate of about one inch a year. Each spring, add an inch of new mulch on top of the old mulch to maintain a depth of three inches. New mulch also makes the area around the tree look crisp and cared for.
Trees add value and curb appeal to your landscape. Proper watering is important in order to keep your tree healthy.
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