Watering Trees in Winter

Most of us don't think about watering our trees right now. It's November, most of the leaves have dropped and the trees look as if they've gone dormant, but the fact is there's still a lot of activity going on underground. Tree roots continue to grow throughout the late fall and winter and because of this, they need moisture to survive. Usually we've had some natural moisture by this time of the year, but it continues to be dry so it's important to water your trees now and throughout the fall and winter months, especially if the weather remains dry and windy. Trees should be watered slowly. Slow watering helps ensure the water will penetrate the ground and not run off. A good rule of thumb to remember is your tree needs about 10 gallons of water per inch of trunk diameter.

Measure the tree trunk's diameter about knee high. In this case, the trunk diameter is 3". Based on 10 gallons of water per inch of trunk diameter, this tree needs 30 gallons of water, each time you water. There are several methods you can use to water your trees. Assuming your sprinkler system is shut off by now, you can use a hand sprinkler, a simple lawn sprinkler, a soil needle or even a 5 gallon bucket with holes drilled in the bottom. Regardless of how you water, the best place to water is around the drip line of the tree. 

The drip line is the point on the ground where water will drip off the widest-reaching branches.

Lawn sprinklers are available in different patterns including circular, square and rectangle. Pick the sprinkler with the pattern that best suits the area you're watering. Place the sprinkler under the drip line of the tree and let it run for 4 - 5 minutes, then move it, following the drip line of the tree.

4 to 5 minutes is the average time it takes to fill a 5 gallon bucket, at low water pressure. You can use this as a gauge to figure out how long you need to let the sprinkler run before you move it. If you need to deliver 30 gallons of water to the tree, move the sprinkler 6 times, letting it run in place for 4 to 5 minutes each time.

If you choose, you can use a soil needle instead of a sprinkler. Work the needle about 8" into the soil, turn on the water on low pressure and let it run. After 4-5 minutes, move the needle about a foot, then push it into the ground. Repeat  this until you've worked around the drip line.

Another technique is to drill ¼" holes in a 5 gallon bucket, set the bucket on the drip line and fill with water. The water will slowly seep out of the bucket and into the ground. If you set 2 or 3 buckets around the dripline, watering will go quickly and effectively.  It is especially important to water trees that are root-limited because they were planted between the sidewalk and the street.

If you can't get to the drip line because of sidewalks or landscape restrictions, you can hand water the area under the tree. Watering during the fall and winter will make a big difference in the long-term health of your trees.