During the fall and winter (October through March) water trees depending on weather, temperature, and soil conditions. You should water in the winter when it is above 40 degrees and when there is no snow cover. Watering your trees is essential during dry periods in the fall, winter, and early spring, when you aren't watering your lawn.
In warm and dry periods in the winter, your water budget will be adjusted to account for some outdoor watering.
Here is a video from the City of Greeley's Forestry Manager Shiloh Hatcher on taking care of your trees in a dry fall and winter.
The Colorado State Forest Service offers the following tips to water your trees.
- Water a wide area. Tree root systems, unlike carrots, may spread two to three times wider than the height of the tree, with most absorbing roots in the top foot of soil. Apply water to soak the entire area within the drip line (the critical root zone directly underneath the full span of a tree’s branches).
- Water slowly. To ensure deep penetration, use a deep root fork (inserted 8 inches or less), soaker hose on low setting or soft spray wand to apply water slowly to the full area within the drip line. Placing a running garden hose against the base of a tree for several minutes is far less effective.
- Trees located in irrigated lawns generally do not require additional water, as long as the area surrounding the tree receives adequate moisture. Conversely, a dry, yellow yard means the roots of any trees present are also dry.
- Trees that do not receive water from sprinkler systems or irrigation require additional water. Every week, apply 10 gallons of water for each inch of tree trunk diameter. Water newly planted trees even more frequently; larger trees, which have extensive root systems, can be watered less frequently.
- Mulch is an inexpensive solution to retain soil moisture and save water. Apply 4 inches of organic mulch onto bare soil within 2 to 3 feet from the base of the trunk (removing any grass first, if necessary). Do not allow the mulch to directly contact the trunk.
Here is a video from GreenCO Colorado with information on the best ways to water your trees and shrubs during a drought or during a dry and warm spell in the fall and winter.