Question: I have planted a new tree on my property. How much should I water to help ensure its survival?

Answer: Providing supplemental water is very important to get new trees established. An important thing to remember is that the tree lost a lot of roots in the transplanting process and all its remaining roots are in a very restricted area. It is important to concentrate your watering efforts on this "root ball," although it is also helpful to water the 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 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 5 gallons of water per week per every inch of stem caliper (trunk diameter measured 6 inches above the ground on young trees).

There are several techniques for proper "deep-watering" of trees including:

• Installation of a drip irrigation system
• Building up a bern around the outer edge of the root-ball to provide a "well" area. Fill it up with water that will slowly soak in.
• Coiling soaker hoses over the root-ball area
• Allowing a garden hose to slowly trickle water onto the target area
• Filling and placing a five-gallon bucket, with four very small holes drilled into the bottom, over the root ball.

A method of preserving soil moisture is to provide a 2" - 3" layer of mulch over the root area. Taper the depth of mulch so that there is no mulch around the tree trunk. A planting diagram showing a mulch layer can be found by clicking here.

Keep the soil moist but not constantly soaked; over water will cause leaves to turn yellow or fall off. Water 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. Continuing watering until mid-fall, tapering off for lower temperatures that require less frequent watering.

The Parks Department has publications available on this topic and many others. For more information on this topic go to the publications list or, contact the Urban Forester.