Why age matters when winterizing trees

Urban trees need different winter care based on their age
Young or old, mulching helps trees retain moisture.

The crisp feeling, cooler temperatures and colors of fall will soon transition into winter. Deciduous trees in the mountains have already prepared for this, as witnessed by their leaves turning yellow and falling. With the coming of shorter days, urban trees also undergo changes in preparation for winter. Tree owners and tree care professionals need to be cognizant of those changes and do their part to ensure their trees make a smooth transition into the winter, and come out healthy and ready to thrive next spring.

[Related: Wilt disease: An emerging risk to planted pines]

Young trees

Tree owners and tree care professionals in cities and towns should take the following steps to help younger trees, or those planted in the past few seasons.

Wrap the trunk. Thin-barked trees like honeylocust, linden and crabapples are susceptible to sunscald and frost cracks because of winter temperature fluctuations. To prevent bark damage, wrap the trunks of younger trees up to the first branches using commercial tree wrap. This is only necessary for the tree’s first three seasons. Remember this rule of thumb for tree wraps: fall on, spring off.

Mulch the base. Apply three to six inches of wood chips, bark or other organic mulch near the base of the tree, but not against it, to reduce soil evaporation and insulate against temperature extremes.

Give them a good drink. Before winterizing the irrigation system, water trees in the area extending from the trunk to the extent of the longest branches. Water slowly, with a sprinkler or soaker hose, at the rate of 10 gallons per inch of tree diameter. Thoroughly wet the top 12 inches of the soil profile.

Old trees

Young trees are not alone when it comes to getting ready for winter, especially following the hot and dry growing season they have just experienced. Some seasonal tips for more mature trees include:

Water widely. Tree root systems can extend up to two times the height of a mature tree. At a minimum, apply water to soak the entire area underneath the full span of a tree’s branches.

Make plans to water in the winter. Following this hot, dry growing season, many trees have been exhibiting signs of stress—especially in western and southern Colorado. Early leaf fall and branch dieback are two common stress symptoms. Winter watering will be a necessity this year, to avoid stressing these trees even more.

Water when it’s warm. The best time for winter watering is on days when snow has melted off and the temperature is above 40 degrees.

Retain and extend mulch. To retain soil moisture and save water, apply up to six inches of organic mulch onto bare soil. Extend mulch as far out from the trunk as can be reasonably maintained, to maximize its benefits and to reduce competition for available water from the lawn or other plants.

[Related: Late winter: The best time to prune trees]

Vince Urbina is an urban and community forestry specialist with the Colorado State Forest Service. He has a B.S. in forestry from Colorado State University, and has been actively managing trees and teaching others about tree care for over 40 years.

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