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.