By Elaine Simmons

As of mid-May, Arlington was officially classified as being in “severe drought,” so our trees are hurting. Without regular downpours, our trees have not gotten the deep watering they need. A root ball can die from the bottom up, so shallow watering is not enough. This means that we must water deeply. There is no “one size fits all” for watering and I have seen a range of instructions. But all agree that young trees need more regular watering than older trees because they lack an established root system. We want their roots to reach down for water, not just spread out. That said, ALL trees need deep watering in times of drought.

Young trees: A good rule of thumb is 10 gallons of water per week for every inch of trunk diameter. That means, for example, that 1-, 1.5-, or 2-inch-thick trees need 10 / 15 / 20 gallons per week, respectively. Some estimates say 25 gallons a week. A 20-gallon water bag lets the water seep out slowly, as does running a soaker hose for hours. But if you only have a regular hose, you can place it a few inches from the trunk and let the water run on low flow. What do we mean by “low flow”? The photo shows a low flow of water that filled up a 2-gallon container in 4 minutes. So, for trees 1-to-2-inch in diameter, you would let the hose run 20 to 40 minutes at a time once a week–easy! Increase the time to 50 minutes in hotter, drier conditions or for larger young trees.

Mature trees: Older trees should be watered weekly in times of drought. A regular hose should be placed further from the trunk than for young trees—at least a foot, extending out to or even slightly beyond the drip line (the outer edge of the canopy). Let the hose run on low flow for at least 30 minutes. I spoil my trees and run it longer.

Other tips: water earlier or later in the day to reduce evaporation and apply mulch 3 inches deep and at least 3 inches from the trunk to help retain moisture and keep the soil cooler.

Trees beautify and cool our neighborhood, so we owe them good care. In addition to your own trees, please consider watering those on county property. And remember that water is much cheaper than removing a neglected, dead tree!