Watering Established Trees
As the summer heat sets in, chances are we’re all pretty tuned in to providing water to our landscape plants. Drip irrigation and other smart ways to hydrate plants are becoming mainstays and people are experiencing success in their landscapes like never before.
Should you water your established trees?
Just because a tree is established doesn’t mean that it doesn’t need any supplemental water. A stubborn blind spot we’re seeing in water care regimens has to do with what are otherwise the anchors of any landscape: established shade trees. These trees often provide the valuable shade coverage that enables the other parts of the landscape to survive the heat. But they themselves often may not receive any focused water care. During cooler parts of the year, these trees can make do because the water delivered to other plants is shared with their extensive root zones, but during the intense heat of summer, even these trees could use a boost.
How should you water an established tree?
People make a common mistake when they do think about watering established trees by placing a hose at the base of the trunk and letting it trickle for an extended period. Unfortunately, this cannot serve the tree as there are no roots in this immediate area that transmit water out of the soil and into the root mass; instead this area, known as the root crown, is the primary anchor point for the tree.
The roots that can move water out of the soil are actually farther away from the trunk than you might think, often only starting in the space midway between the trunk and the edge of the tree’s canopy, known as the drip line. In fact, these roots can extend out to at least twice the width of the canopy, creating a root network that is often bigger than the tree itself.
Therefore, to meaningfully provide water to an established tree, you need to water the root zone that starts just inside the drip line and out to beyond the canopy itself. A full sized soaker hose extended around the tree in a zig zag is the ideal way to do this so that water is delivered to the full circumference. Otherwise, placing a hose end sprinkler in four different quadrants around the tree will suffice.
How much water does an established tree need?
The duration of watering is also important. If the tree is in a lawn that receives spray irrigation, that may not be enough water either. Be prepared to run the soaker hose for an extended period of time to deliver enough water to make a difference. Generally, delivering two inches of water is recommended, so this might mean you’re running the water for multiple hours. Be sure to set a timer so you don’t lose track. If you’re using a hose end sprinkler, use a rain gauge (or an old tuna can) to help you track when you’ve delivered the requisite two inches of water.
Some trees will require more frequent watering throughout the Summer to cope with the heat. Japanese Maples need more regular watering, for example, because they are more susceptible to heat and drought stress.
