It can take up to two years for drought conditions to show up in trees. Symptoms include wilting, curling and yellowing leaves. Deciduous leaves may scorch, become brown on the edges or brown between veins. During continued drought, leaves may be smaller than normal, drop prematurely or remain attached to the tree even though brown.
Drought-inflicted evergreen needles may turn yellow, red or purple. They may also turn brown at the tips of the needles, and browning may progress through the needle toward the twig. Drought may not kill a tree outright, but lead to serious secondary insect and disease infestations in following years.
Experts recommend deep water for trees to a depth of 12 inches below the soil surface. Contractors should 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 three to five feet beyond the dripline on all sides of the tree.
Contractors should water slowly to disperse the flow of water to get the water down to the roots. Watering for short periods of time 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.
It’s tough to know exactly how much water established trees need, but as a general rule, small- and medium-sized trees use approximately 10 gallons of water per inch of trunk diameter at knee height.
Mulching around trees with 4 inches of organic mulch can help reduce moisture loss as well. Contractors can use wood chips, shredded bark, leaves or evergreen needles. Rocks are not good because they increase temperatures and moisture loss from leaves and stems.
Keeping trees healthy and pest free also reduces their need for water. Postpone any construction activities planned near your tree to reduce impact to roots. Correct pruning is also important. Leaving broken, dead, insect-infested or diseased branches can further weaken a tree during drought and lead to deadly secondary insect and disease problems.
Source: Watersaver.org
