By Carol Gilmore, Colorado Master Gardener
Colorado has had some crazy weather over the last year and the plants in our landscapes have suffered. First, there was the 50°F temperature drop in October 2019, followed by an extremely dry winter. Then there was another large temperature drop in April that killed a lot of buds just coming out on the trees and some new leaf growth. That further stressed the trees and other plants. The summer of 2020 has been close to record hot temperatures with a record number of 90°F days and a severe drought in most of the state. The large temperature drop in the second week of September did further damage to plants.
Many trees in our landscapes are suffering from these stressors and could use some extra care through these drought-stricken times.
Winter watering should be done every winter, but especially now. After your sprinkler systems have been shut down, water your landscape during extended dry periods, when the temperature is above 40°F and there is no snow cover. Water early in the day to allow it to soak in and check to make sure that it doesn’t run off. Water should reach a depth of 12 inches. Trees and shrubs should be mulched to preserve moisture and prevent drying out.
Use a sprinkler, a soaker hose or a deep-root needle or fork for winter watering. A needle should be inserted to a depth of approximately eight inches. It should be placed near the drip line in one-foot increments with a timing of one minute at each site using a grid pattern inside and outside of that drip line. Whatever method of watering you use, water should soak into the soil to a depth of approximately 12 inches for trees. Watering should be done halfway to the trunk from the edge of the branches and then two to three times that distance out from the edge of the branches.
Watering recommendations suggest watering at least three times during September and once or twice per month from October to March, depending on how much precipitation is received. Younger trees and evergreens require more water. On average, trees need 10 gallons of water per diameter inch of trunk per month in the winter.
Newly planted trees, shrubs, perennials and grasses need the extra water over winter to help them become established and grow the root systems they need to survive. Newly planted lawns also require extra winter watering. Mulch will help the soil retain moisture and is best applied to a depth of approximately three to four inches. Mulch around trees should extend two to four feet out from the trunk or to the drip line and should be kept away from the trunk of the tree.
For more information, please see the following science-based references: