A common question we hear, especially since it seems like we will never get rain here again, is how much water do trees need. Short answer: it depends. Long answer follows, but first, do not rely on lawn sprinkler systems to adequately water your trees and shrubs!
After planting, the most important thing for any plant is to receive regular watering. There is not a set schedule for watering frequency as environmental conditions — soil type, sun exposure, topography, daytime and nighttime temperatures, wind, and humidity — combined with botanical conditions — type of plant, amount of leaves on the plant, size of the plant roots, age of the plant, etc. — all determine how quickly the plant uses the water available to it and when it needs watering.
Never water automatically without first checking the soil to determine if watering is needed. For trees, stick a 10-inch screwdriver in the ground as far as you can, if it’s hard to push in — water; if it’s easy — wait.
Plants in sandy soils will need to be watered more frequently than those in clay soils. Watering deeply, thoroughly and only as needed will encourage a deep and healthy root system that enables plants to withstand environmental stresses. Avoid watering on or through the foliage. Do not rely on lawn sprinkler systems to adequately water your trees and shrubs.
Soaker hoses, drip irrigation systems, specialized water bags, dedicated hose sprinklers — that attach to the hose end, NOT the underground lawn irrigation system — or hoses dribbling water are all good options.
A recently planted bare root tree needs a pint to a quart of water daily, a newly planted 5-foot tall ornamental tree needs 2-3 gallons per day and most established trees with trunks 2 inches or more in diameter will need 20 gallons of water weekly, especially in hot, windy periods. For established trees, deposit two inches of water each time. To measure watering depth using a dedicated hose sprinkler, place several empty containers, like deep dish pie tins or plastic cups, in the radius of your lawn sprinkler. When the average depth in the containers is two inches, you’ve adequately watered your tree and encouraged strong root growth.
Some tree roots are at least as far away from the trunk as the tree is tall. The critical watering distance from the trunk is two-thirds the height of the tree. So for a 30-foot tall tree, the critical watering area is a circle 20 feet away from the trunk.
As the plant matures and depending on what type of plant it is the watering regime may change. For the first several weeks if not months after planting, all plants will need regular watering attention and the only way to tell if your newly planted plant needs water is to check the soil moisture with your finger or screwdriver.
And if I haven’t said it before, I’ll say it now: Do not rely on lawn sprinkler systems to adequately water your trees and shrubs.
Art Smith is a co-owner of East Pierre Landscape and Garden Center, 5400 SD Hwy 34, Pierre