How to Water Your Trees
Trees are a valuable part of your landscape. They shade your home, lowering your energy bills and cool your garden so both you and your flowers will be happier. Trees benefit from irrigation when rainfall is not abundant. Droughts can weaken your tree leading to pest problems or dying branches which can eventually lead to tree death. Once you start watering you should continue to do so on a consistent schedule until rain comes.
The best way to water a tree is with soaker hoses or drip irrigation. Sprinklers are less efficient. Deep watering to a depth of 15 inches, once a week is ideal during the growing season when drought exists. Watering deeper wastes water. Watering more often can lead to disease and insect problems and is also harmful to your soil's health and leaches nutrients out of your soil. Trees should be watered on their own schedule and separated from other garden plants so as to prevent over-watering. Tree roots needs oxygen to function properly and too much water fills all the spaces in the soil, not allowing room for the oxygen. Watering too often encourages shallow rooting which can lead to drought damage later on, and also wastes water. Wetting the foliage may encourage insects and disease.
It is best to water the soil directly under the foliage and not past the drip line, except on newly planted trees. Do not wet the trunk or water within 2 feet of the base of the tree, and do not wet the foliage. The best time to water is at night followed by early evening.
Newly planted trees need water applied right over the root ball and a few feet farther out as well. If you have built a water dam extending out a couple of feet from the original root ball then fill this up twice and do not water more often than every 3 days to get a tree established.
Trees should also be watered in winter, during droughts, as they also lose moisture when they are dormant. Much less water is needed at this time and they should not be watered during very cold periods when soil temperatures are near freezing.