Watering Trees

Commonly in Illinois there are periods of drought. During these times trees need to be given special attention and monitoring.  

Symptoms of drought include:

     - wilted foliage

     - a sparse canopy of off-colored and undersized leaves

     - leaf scorch

     - yellowing of the leaves

     - leaf drop and premature leaf color

Check the soil before and after watering.

If there are cracks in the soil you will know that the soil is lacking moisture but dig down about 6-12 inches to verify whether or not there is moisture.  Too much watering can be as bad as not enough watering. When the soil is without moisture, water the tree.  Soil will generally dry out within 7 to 10 days of not having a good soaking rain.  So you can also use the 7 to 10 day guideline for providing a good deep soaking watering of your trees.

Since not all soils and not all terrain is alike you may need to use different techniques to get the job done. Trees planted on a slope may need some type of soaker hose or drip emitter to reduce run-off and allow for water infiltration.  Trees in sandy soils may need shorter and more frequent watering regimes. trees in clay soils may need longer watering intervals. Be careful with clay soils that their slower infiltration rate doesn't fool you into thinking that the soil is saturated. Always go back to the basic digging down to see how deep the water has gone. It is always advisable to physically check the soil moisture by going down to a one foot depth and visually seeing moist soil.

Tree Age vs. Watering Regime Tree age does matter to a degree but all trees need to be watered during a drought. The age of the tree will determine where and when to water.

     Watering Newly Planted Trees. During the first couple of years after being planted, you new tree will be expending a lot of energy trying to get its root system established. A newly planted tree can also go through transplant shock. Research shows that it takes one year for each inch of trunk diameter for the tree to get through this transplant shock. Because of these stresses, young newly planted trees may show symptoms of drought more readily than older more established trees. For the first few months after planting, the tree's roots will be contained very close to the original root ball. Watering the tree should be closer to the trunk and original root ball plus 2- 4 feet out to encourage the outward growth of the tree roots. After a few months of tree growth, you should expand the watering zone to the entire tree canopy plus an additional 2-4 feet out. It can take up to two years for the tree roots to move into the surrounding soil.  Watch newly planted trees for symptoms of leaf wilt. This will tell you if you need to water the tree more often than the 7 day interval. Mulching and adequate watering during this time can help the tree survive.

     Watering Mature Established Trees  A mature trees roots are about 2 feet deep and 90% are within the drip line of the tree's canopy.  When watering established trees, it is important to provide a deep soaking irrigation within the entire area beneath the tree canopy and extending several feet beyond the drip line. Do not water directly around the tree trunk of an established tree. An easy way to tell if the water has soaked deeply is to use an 8 to 12 inch screwdriver or probe and penetrate it into the ground. It will readily move through the moist soil but will provide resistance in the drier soil.  It is important to not under water a tree.  Under watering a tree will encourage feeder root to grow close to the surface and since the soil dries from the top down, these newer delicate roots will be the first to die.  This makes the tree use its energy reserves to re-establish more feeder roots.  This will make your tree less drought tolerant in the long run.

RIGHT TREE RIGHT LOCATION

Some long term planning can help you combat drought.  Tree species have differing levels of water tolerance. Some trees like xeric or drier conditions while other like mesic or moist conditions. By selecting a tree that matches your climate and soil conditions you can help sustain a healthier community forest.  Knowing your trees drought tolerance will also help you determine what watering regime is best for your tree.

Some Drought - Tolerant Tree Species include:

Thornless Honeylocust

Zelkova

Kentucky Coffeetree

Bur Oak

Some High Moisture Species include:

Bald Cypress

Shellbark Hickory

Red Maple

Silver Maple

River Birch

Weeping Willow

Cottonwood

Boxelder

Other Tree Care tips during a Drought:

1) Do not apply fertilizer to drought stressed trees when water supplies are limited. Applying fertilizer encourages more flushes of growth which are high water demand functions for a tree. Many fertilizers also contain salts that can do harm to drought stressed roots. Especially avoid high nitrogen fertilizers or weed and feed products during droughts.

2) Don't do any heavy pruning. However it is ok to remove storm damaged, broken, insect-diseased infected branches at any time.

3) Keep an eye out for insect and diseases since drought stress can make trees more vulnerable.

4) Contact a professional forester, extension horticulturalist or certified arborist should insect or disease issues arise.

Check out the IDNR Urban and Community Forestry VIDEO section on Tree Watering