Protecting your trees for winter

V.J. Comai

Winters in Vermont can test even the hardiest of souls, and can also be detrimental to the health of your trees. In preparation for the long cold months, protect your trees to ensure that they will begin the growing season unscathed and healthy.

Evergreens are prone to winter injury, which appears as a browning or scorching of needles, usually occurring from the needle tips downward and often referred to as winterburn. Recently planted trees that are not well established are particularly susceptible. This type of injury can be attributed to desiccation or loss of water due to sun and wind, as the trees are unable to replenish the loss when water in the stems and roots is frozen.

Research proves that commercially available products that claim to prevent this type of injury are largely ineffective. The best protection is a physical barrier made of burlap, or shade cloth, that is wrapped around the trees. Keeping trees well-watered up until the ground freezes is also strongly advised.

Frost cracks can be a serious problem on younger trees with thin bark, such as crabapples, maples, lindens and willows, most often on the south or southwest side of the tree. Bark heated by the winter sun, followed by a sudden drop in temperature, causes the outer layer of wood to contract more rapidly than the inner layer, resulting in long vertical cracks.

Wrapping trunks of susceptible trees up to the first branches with a white geo textile tree wrap will reflect the sun, preventing extreme temperature fluctuations. The wrap should be removed in the spring. Sunscald can also be prevented with a trunk wrap.

Voles, mice, rabbits, and deer can devastate younger landscape trees that are left unprotected. Mice and voles will girdle trees by feeding on the bark near ground level, while rabbits will feed above the snow line. Trees surrounded by heavy grass, weed cover, or mulch, or those located near property edges that provide habitat and cover for these small mammals, are most vulnerable, so removing thick vegetation near the base of young trees is advised.

The most effective deterrent to girdling by mice and rabbits is to wrap the lower trunk from ground level up to a height of 24-30 inches with hardware cloth, or wire mesh with ¼-inch or smaller openings that can be attached around the tree using plastic zip ties. This wrap should be removed in early summer or adjusted as the tree grows in diameter.

Deer are increasingly a problem due to the ongoing fragmentation and reduction of their natural habitat. There are numerous commercial deer repellent products available that are applied to the foliage, twigs, and stems of trees and shrubs and deter feeding due to their foul odor, bitter taste, or a scent that instills fear such as predator urine.

To be most effective, deer repellents should be applied prior to the deer establishing a regular feeding pattern and need to be reapplied throughout the season based on frequency of rainfall and the specifications on the product label. Physical barriers such as chicken wire fencing or burlap attached to stakes close to small trees may be a more practical and cost-effective method of control.

While winter appears to be here to stay, it’s not too late to invest some time to ensure that your trees emerge from the long winter in the best shape possible to begin the new growing season.

Do you have a question that you would like to have addressed in Tree Top-ics? Email your question to vcomai@bartlett.com.

V.J. Comai resides in Charlotte and works as an arborist representative for Bartlett Tree Experts. For nearly 25 years he has managed the South Forty Nursery in Charlotte where he grew field produced trees and shrubs for the wholesale market. He is a certified arborist with the International Society of Arboriculture, (ISA) a past president of Green Works, The Vermont Nursery and Landscape Association.

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