Watering Trees

Periods of drought are common on Colorado’s Front Range. This area is naturally a semi-arid, shortgrass prairie that would have few trees without irrigation. Growing trees here is difficult in wet years let alone in drought years. Drought makes growing healthy trees in this region all the more challenging and reinforces the value of a majestic shade tree.

Where do I water my tree?

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 lead to more drought damage.  Don’t dig holes in the ground in an effort to water deeply. This dries out roots even more. A soil needle/deep root feeder attached to a hose is acceptable to insert into the ground if your soil is not too hard and compact.  Overhead spraying of tree leaves is inefficient and should be avoided. Watering at ground level to avoid throwing water in the air is more efficient.

Tree Watering: Amount of Water Needed & Methods to Use

Caring for trees requires different watering methods than your lawn. During water restrictions, irrigation systems designed to water turf do not sufficiently water your trees. During the drought, trees should be given a higher priority than lawns. Lawns can be replaced in a matter of months whereas a 20 year old tree will take 20 years to replace.

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.

Even in years when drought is not a concern – winter watering is crucial, especially with evergreen trees! Well-timed fall and winter watering may allow a tree to survive on less water than a regime of plentiful water applications during the growing season. Tree roots continue to grow throughout the winter and need moisture to survive. Generally, water one to two times per month October through March on a warm day when the ground is not frozen. Use the same amount of water as during the summer months.
Source:  watersaver.org