BigTreeSupply.com: Irrigation Basics

Proper watering practices are vital to the survival of a newly planted tree. One of the most common causes of decline in newly planted trees is improper irrigation. Improper irrigation can be either too much water or too little water, and the symptoms of stress that you get in either can be indistinguishable. So, proper irrigation requires a little investigation, continued monitoring and adjustments when necessary.



There are several things that rrigation amount and frequency are dependent on:

• Air Temperature

• Soil Texture

• Soil Structure

• Tree Species

• Season



With so many factors, it is difficult to give an irrigation standard that is appropriate for all trees and landscapes. Generally, no irrigation is needed when trees are dormant. The period of dormancy for deciduous trees is easy to determine because they lose their leaves. Evergreens go dormant also, but as there is no visible sign of when this occurs you should use deciduous trees as indicators for the dormancy period for both types of trees.



Irrigation should begin when deciduous trees start to bud up or leaf out in early spring. The most amount of water to use will be required mid to late summer when soil moisture has been reduced and air temperatures are at their highest. In mid to late fall the irrigation schedule can be tapered off, back to a watering schedule that was used in early spring. Once fall leaf drop occurs discontinue watering until the next growing season.



I highly recommend that trees be irrigated with automated drip irrigation. This type of system can be as simple as a soaker hose attached to a battery operated watering timer. Drip irrigation uses the least amount of water with the highest efficiency. It evenly distributes water directly over the rootball of newly installed trees and it provides consistent moisture levels.



So how do you know if you have achieved the right irrigation frequency and timing?



One simple method that gives good results requires some investigation: Use a trowel to dig down at the root zone approximately 4-6". Pick up a small handful of soil and squeeze it tightly in the palm of your hand. If the soil has formed slightly to the shape of your palm after you have opened your fist, the soil moisture is ideal. If the soil easily crumbles and falls apart the moisture level is too low, and if you are able to squeeze water from the soil when it is in your fist, the soil is too wet. All water should be absorbed within 6 hours, and no puddling should occur in the root zone.



Trees absorb both oxygen and water from the soil. Overly saturated soils have little available oxygen and soils that are too dry hold any moisture so tightly that it is unavailable to trees. It is a fine balance that requires continued monitoring and adjustments.



If you have any questions regarding the irrigation of newly planted trees make sure you contact a tree expert to ensure you give the trees the best start possible.



Ross Latham is owner of Big Trees Inc. (http://www.bigtreesupply.com) in Snohomish, WA, one of the largest Seattle tree nurseries with over 300 varieties--spring flowering, evergreen, privacy, young & mature trees and specializing in tree transplanting. See their blog at http://www.bigtreeblog.com.