Water – Trees Can’t Live Without It, But It Can Kill Them

We are having a dry spring so far and the trees need water as they begin the spring flush of growth. It would be a good idea to give the trees in your landscape a good soaking during this period of dry weather.

This brings up the topic of proper irrigation (or watering) of your trees. It is very important to do it right. Many trees are killed with improper irrigation, mostly from over watering and keeping the top layer of soil saturated. The proper way to irrigate your trees is to provide a good, soaking irrigation that penetrates the top layer of soil and moves down into the layers underneath the top 3 inches. It takes about 3/4 – 1 inch of water in the root zone of the trees to penetrate deeply. This is a fair amount of water, equal to a good soaking rain. The trees should get this type of irrigation every week or ten days during the growing season, in the absence of rain. A drying cycle should occur between waterings. Tree roots (and all plants) need oxygen in the soil and the drying cycle allows for good gas exchange between the soil and the atmosphere. Without oxygen, tree roots die.

To accomplish good irrigation, without having half of the water run off and down the street, the irrigation should take place over enough time to allow the water to soak in. The best method for irrigation with an automatic sprinkler system is to set the controller to go through the zones multiple times. For example, if it takes your system 45 minutes of run time per zone to put out 1 inch of water, then set the controller to go through each zone three times for 15 minutes each time. The first time through will break the surface tension of the soil and allow the subsequent cycles throught the zones to soak in well.

The goal of irrigation is to put a substantial amount of water on the root zone of the trees and then allow for a drying cycle before the next watering. Landscapes should not be watered every day or every other day. Watering once per week, with a good deep watering is very adequate for most landscapes. The trees will love it and so will your turf and shrubs. You will have less problems with fungal and bacterial disease issues and the plants will thrive with their roots down deep.

Scott Geer

Scott Geer

Scott Geer has a master's degree in forestry from Stephen F. Austin State University and is an ISA Board Certified Master Arborist.® He is also a graduate of the American Society of Consulting Arborists Academy.