Typically, cold snowy winters and cool, relatively dry summers are the normal for weather patterns in Summit and Eagle Counties.  We usually see about 20-24 inches annual precipitation, of most of which comes as snow in the winter.  The weather over the last few years has not been exactly typical.  The winter snowfall has been below normal and the summers seem a bit warmer than usual.  Most of our summer rainstorms, when we get them,  have been fast and furious rather than a slow rain that can soak into the soil.

This drought-like weather pattern has raised havoc on many of our trees.  Trees of all ages and histories are showing signs of drought injury.

Symptoms of drought injury to trees can be sudden or take up to two years to be revealed!  Typically, leaves may wilt and scorch, fall early in the season and make the tree appear thin and sickly.  Evergreen trees may exhibit drought stress as brown needles at their tops and ends of lateral branches.  Often times, drought stress may not kill a tree outright, but set it up for more serious secondary insect and disease infestations.  So, what can we do to preserve the health and value of the trees in our landscape when water restrictions are commonplace and conservation of this precious resource is critical?  Following the below listed tree maintenance procedures during drought periods can significantly increase a tree’s chance of making it through low moisture times and allowing it to continue to be a valuable part of the landscape for years to come.

For existing plant materials requiring regular watering, remove water-loving bluegrass from the base of the tree or shrub out to its dripline.  Removal can be done with non-selective herbicides (such as Round-Up) or the grass can be mechanically removed.  Be careful not to damage surface roots of the shrub or tree if mechanically removing the sod.  Replace the grass with two to four inches of wood chip mulch.  The mulch will not compete for water like the pre-existing grass.  It will also keep the lawn mower and weed-eater at a distance from damaging tree bark and will insulate the soil from temperature extremes.  Over time the mulch will break down adding nutrients to the soil.  The decomposition can improve soil structure, aeration and water penetration. Most important, mulch helps retain moisture in the soil for longer periods between watering and rainfall. 

Young or newly planted trees and shrubs require more frequent watering than mature, established trees.  Drip irrigation systems are efficient at applying the proper amounts of moisture to newly planted trees and shrubs, while not wasting large amounts of water that above ground spray irrigation systems do.   Watering every two to three days during our summer months is critical for new trees to establish.  Be sure to frequently check soil moisture levels with a trowel or pointed tool and only apply water when soil conditions warrant.

Established and mature trees and shrubs need less frequent watering and can withstand drought conditions better than new plant material.  However, it is important to add supplemental water to these plant materials as well, since they can be quite valuable specimens in the landscape and take longer for drought injury to appear.  Apply water every three feet within the tree’s absorbing root zone, which generally extends from just within the tree’s canopy to beyond its dripline.  Soaking the tree with drip system or manually by hose once a week during the summer months should be sufficient to maintain the tree’s health.  Apply the moisture at a slow rate to allow deep soaking, and to avoid run-off, approximating about an inch of moisture per week.  Check the soil moisture just like you would for the young tree.

Minimize fertilizer applications during time of drought, as these may stimulate too much top growth resulting in too much leaf area on the plant for the root system to maintain during periods of limited soil moisture. It is ok to use root-stimulating fertilizers or mycorrhizae inoculate that do not promote leaf growth. Properly prune trees and shrubs during time of drought to improve structure, limb stability and to remove dead and weakened branches.  Leaving broken, dead, insect-infested or diseased branches can further weaken a tree during drought and set the tree up for deadly secondary insect and disease problems.

Follow these guidelines to help your trees through this period of drought.  After all, Trees are a renewable resource, but who wants to wait care for what you have!