Give young trees a little TLC
As a result of city growth, Coeur d'Alene has many newly-planted trees. The city's street tree inventory shows that about half of the city's street trees are less than two inches in diameter. Young trees, like young people, need a little extra care to get off to a good start.
Providing supplemental water is very important to getting new trees established. An important thing to remember is that your young tree lost a lot of its root structure during the transplanting process and that all of its remaining roots are in a very restricted area. It is important to concentrate watering efforts on this "root ball."
It is also helpful to water the immediately surrounding area to encourage new root growth beyond the root ball.
If natural rainfall equals an inch of water every week, additional water may not be needed. However, when natural rainfall drops below that amount, start giving the tree some additional water. Don't just rely on lawn sprinkling to provide adequate water to your young trees - it usually does not water deeply enough. A good rule of thumb to follow is to provide five gallons of water per week for every inch of stem caliper (trunk diameter measured six inches above the ground on young trees). This amount should be adjusted for factors such as soil porosity and high temperatures.
There are several techniques for proper "deep-watering" of trees including:
• Installation of a drip irrigation system.
• Building up a berm around the outer edge of the root-ball to provide a "well" area, filling it up with water that will slowly soak in.
• Coiling soaker hoses over the root-ball area and just beyond.
• Allowing a garden hose to very slowly trickle water onto the target area.
• Drilling four, very small (1/16") holes in a five-gallon bucket; place over the root ball and fill, allowing to drip out slowly.
Providing extra water should be done for several years. A general rule is to water one year for each inch in diameter (measured 6" above the ground) of size, plus one more year. For instance, a tree with 2" of diameter should be given supplemental water for three years.
A good method of preserving soil moisture is to provide a 2- to 3-inch layer of mulch over the root area. Taper the depth of mulch so that there is no mulch touching the tree trunk. Do not mulch deeper than 3 inches as this can cause problems. Mulch also provides nutrients and keeps the root area cool in the hot summer months.
Keep the soil moist but not constantly soaked. Over-watering will cause leaves to turn yellow or fall off and can cause the tree to fail. Water new trees deeply at least once a week - barring rain - and more frequently during hot weather. Watch your tree's "body language."
When leaves droop and wilt, a tree is telling you it does not have enough water available to the roots. Continue watering until mid-fall, tapering off as temperatures get lower and the trees require less water.
The Coeur d'Alene Parks Department has publications available on this and other tree care topics. They are available at the Parks Department office at City Hall (710 E. Mullan Avenue).
For more information on this topic, visit the city website at http://www.cdaid.org/urban/index.html or call the Urban Forestry division at 769-2266.