July 11, 2018

Protect your investment in new trees: water them!

Summer is upon us in the Pacific Northwest, and that means it’s time to keep a careful eye on your newly planted trees (those that were planted in the last 3-5 years). The process of being transplanted is stressful, and your new tree doesn’t yet have the roots it needs to be self-sufficient.

So, how much should you water? There’s no hard-and-fast rule for watering trees. How much water the tree needs depends on the kind of tree it is, the soil it’s planted in, and the microclimate around it. Here are a few tips:

• Start with about 10 gallons per week for every 1” of caliper (“caliper” is the width of your tree’s trunk, measured 6” above the soil line). So, if your new tree is 1.5” in diameter at its base, start with 15 gallons per week.
• Water your tree deeply, so that the entire area where the roots are (the “root zone”) is moistened, not just the surface. A temporary berm (or raised barrier) at the tree’s dripline (the area directly under the outer circumference of the branches) helps to direct water to the roots while the tree is young. You can break this berm down after a few summers.
• Mulch under and around the tree to help keep the soil moist and cool. Mulch should be 3-4” deep. Do not pile mulch against the trunk!  It’s a good idea to keep mulch around the tree for life.
• Don’t overwater or underwater! Keep the soil moist like a wrung-out sponge. Before you water, take a hand tool and dig down a couple of inches. Is the soil still moist? No need to water. Is the soil bone-dry? Try increasing the amount of water slightly, add a berm to capture water, or add mulch to retain it (see above).
• During those times when it is particularly hot and dry for an extended period, you might need to water the tree more than once a week.  If the leaves begin to wilt and the soil is dry, an extra watering day might be just what the tree needs.

All you need to water a tree is a bucket! Water your tree deeply so that the entire root zone is moistened, not just the surface.