Water Requirement Factors

A tree’s water requirements depend on several factors, including climate, size, soil and species. A sudden change from cool to hot weather can leave a tree short of water. Trees should have an adequate supply of water and should not be left to dry out.

Naturally, large trees need more water than smaller trees, but species can be a determining factor despite size comparisons. For example, fruit-bearing trees may require more water than more established larger trees. Newly planted trees require less water than mature trees, but young trees need to be irrigated more often. Newly planted trees that are inadequately watered will usually stop growing and remain stunted the rest of the season. One of the most important reasons for carefully irrigating young trees is to develop a deep and extensive root system early on.

It is important to determine soil type and depth in considering water requirements. (If you are not sure of the water-holding capacity of your soil, contact your local Natural Resources Conservation Service work unit for an evaluation). Sandy soils can store only about 1 inch of water per foot of depth, while clay soils store about 2.7 inches of water per foot of depth and loams, which are a mixture of sands, clays and silts, will fall between these ranges. In general, trees planted in sandy soils require more frequent irrigation as these soils do not retain water very well. But, clay soils require less frequent irrigations with larger amounts of water to thoroughly wet the soil.

Most of the roots that absorb water and nutrients are out as far as the ends of the branches, or dripline, and beyond. Therefore, it is important that water is applied in this area as well as near the base of the tree. A good method is to form a basin under the tree and fill it with water every 10 to 20 days, depending on climate and soil type. The basin should be 3 to 6 inches deep and extend from the dripline nearly to the trunk. Be careful to keep water 12 to 18 inches away from the trunk due to soil borne fungus diseases, such as crown rot, which is fostered by keeping the soil at the trunk too wet.

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