Properly Watering Your Trees

All living things need water to survive, from bacteria to giant Sequoias. All organisms, plants, and animals use water: salty or fresh, hot or cold, massive amounts of water, or almost no water at all. Without water, life would not exist.

This year’s spring season has offered little rainfall to mention. Chicago and surrounding suburbs are firmly in a drought. It is unknown whether this dry weather pattern will change anytime soon. Providing supplemental water when rainfall is scarce, to your trees and woody ornamentals, is essential in keeping them healthy and stress-free.

It is important to remember, every physiological process a tree experience depends on water. Without adequate soil moisture, trees become stressed making them more susceptible to conditions that can have damaging short-term and long-term effects on their health. To name a few, drought-stressed trees are more likely to experience slower growth, leaves can be dwarfed in size and discolored, disease and insect problems have the potential to increase, leaf-drop can occur, and with severe water deficits branches begin to die. It is also important to keep in mind, water provided will not only support your tree during the current growing season, but it ensures next year’s canopy growth will be lush and full of leaves. Mid-summer, many tree species produce the buds for their foliage that will develop next spring. If there is not enough water during this process of bud development, trees may set a lower number of buds, and bud development may be compromised impacting how well trees performs next year.

Keeping a few simple watering rules in mind will ensuring your trees will continue growing strong and will promote good health for seasons to come. Soil should be kept consistently moist; avoid allowing the soil to dry out and avoid allowing the soil to become soggy. Aim to have your trees receive one inch of water per week (1”/wk); be sure to take into account natural precipitation. The frequency of watering will be dependent on factors such as daily temperature, soil drainage, and exposure to direct sun. The best way to determine when trees need water is to physically check the soil. Using a garden trowel, dig to a depth of five to six inches (5” – 6”). If the soil is dry to the touch, water is needed.

Trees prefer deep infrequent soakings, rather than short frequent watering cycles which is typical for watering turf. Do not rely on your sprinklers or irrigation system used to water your lawn. While they are very convenient, rarely are they ran long enough to have the water reach the fine, water-absorbing roots. Most tree roots can be found in the top twelve to eighteen inches (12” – 18”) of the soil profile. Sprinklers often wet the foliage of trees, as well. There is no reason to water the foliage of trees, and in some instances, may lead to unwanted disease outbreak.

Using a garden hose, set on low-flow pressure, is quite effective for properly watering trees. Water where the roots are located. Focus on the dripline of trees, from the trunk out to the end of the branches. Let the garden hose run slowly for a bit and move it around occasionally until the entire root system has received water. Avoid watering just at the base of the tree, although with smaller trees this may be your only option. Prior to subsequent watering, be sure to check the soil using a garden trowel, digging to a depth of five to six inches (5” – 6”) to determine if supplemental water is needed.

If you have recently installed a new tree (within the last 3 – 5 years), proper watering is the most important factor towards tree establishment. Newly planted trees need to establish their root system. Check the soil moisture for new trees every day; however, most times they will not need to be watered every day. Young trees draw most of their moisture from the root ball. The root ball can dry out quickly, even when the surrounding soil remains moist. Surrounding soil can wick moisture away from the root ball, if dry. When the soil is drying, be sure to water thoroughly, to the entire root system (root ball), and the surrounding area, if needed. Irrigation bags are a good option for young trees. Once the bag is filled, the water comes out slowly from the bottom of the bag, going directly into the soil around the roots.

Do not forget about large mature trees; they require water too. Tree roots of mature trees are supplying water to a very large plant. Mature trees will have a very extensive, wide-spreading root system. These large root systems are necessary to sustain and support tree health. If some of these roots are in dry soil, they are not contributing to the water supply and the trees will not be getting as much water as they need, putting them under stress.

Try not to overlook the importance of watering parkway trees; they too need water during droughts. Many parkway trees provide great benefits to neighborhoods in the way of shading homes and recreational areas, providing a sense of establishment, increasing property value, and helping with sewer water management.

Be sure to monitor soil moisture well into the fall and provide water to your trees when warranted. Trees and shrubs, especially evergreens and newly planted trees, need ample water in their root systems going into winter. Although many trees will appear dormant, they continue to require our attention up until the ground freezes. Water as long as you can.