Tree watering rules of thumb
• Water trees three times a month in addition to watering your lawn.
• Deep watering to a depth of 12” inches below the soil surface is recommended. Saturate the soil around the tree within the “dripline” (the outer edges of the tree’s branches) to disperse water down toward the roots.
• For evergreens, water 3’-5’ beyond the dripline on all sides of the tree.
• The objective is to water slowly, dispersing the flow of water to get the water deep down to the trees roots. Watering for short periods of time only encourages shallow rooting which can shorten tree longevity. Don’t dig holes in the ground in an effort to water deeply. Digging holes dries out the root system.
• Overhead spraying of tree leaves is inefficient and should be avoided. Watering at ground level to avoid evaporation is the most efficient.
• How much water your tree should receive depends upon the tree size. A general rule of thumb is to use approximately 10 gallons of water per inch of trunk diameter for each watering. Measure trunk diameter at knee height. General formula: Tree Diameter x 5 minutes = Total Watering Time. Example: When you hand water using a hose at medium pressure, it will take approximately 5 minutes to produce 10 gallons of water. If you have a 4” diameter tree, it should receive 40 gallons of water - multiply by 5 minutes to equal total watering time of 20 minutes.
• Shelterbelt irrigation may be helpful during unusual drought periods or for older stressed windbreaks. Be sure watering is adequate to drain deeply into the soil (at least four feet). If the trees are not watered deeply, salt buildup in the shallow rooting zone could eventually damage the shelterbelt (Peter Kolb, 2016)
• Water absorption and holding capacity of soil varies with texture. Sandy soils (feel gritty and soils don’t stick together when rubbed between fingers) allow for quick water infiltration but can’t store much water since large pores allow most to filter away. Clay soils (stick or greasy when wet, very hard when dry) do not allow water to infiltrate very easily, resist root expansion and tend to hold onto water so tightly that trees can’t absorb it. Silty and loamy soils (can make crumbly pancakes or sausages when moist but not sticky)
are the optimal soils for growing plants as they allow water to infiltrate and hold it in a plant available state (Peter Kolb, 2016)
Information for this article was taken from CSU Extension and Peter Kolb, MSU Forestry Specialist. For additional horticultural management, please contact the Chouteau County Extension office at 622-3751, or stop by for a visit in the courthouse basement.
Montana State University U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action provider of educational outreach.
