Do you know how lumberjacks know how many trees they’ve cut down? They keep a log.
Dad jokes aside, trees are a valuable resource that take years to reach full potential. Apple trees take an average of five years to begin fruiting, sometimes longer. Shade trees require a decade or more before their canopy is large enough to cast much shade.
Trees are all the more precious because they do require years of patient growth. In the meantime, we can partner with our trees to give them every possible advantage, and one of the prime ways is by protecting them for the winter. Years of growth can be ruined in minutes as rabbits, deer and voles can quickly kill a tree while gnawing bark as a winter food source. Sunscald and bark cracks can ruin a tree in just one winter.
Young trees are particularly vulnerable during the first five years following planting. Their bark is thin and easily damaged during winter, and thin, smooth, tender bark is an attractive food source. Fruit trees are especially vulnerable, as their bark remains thin well past the onset of fruit bearing, and the bark and twigs contain compounds flavorful to animals and rodents.
The following are measures to protect our trees for the winter.
- If younger trees aren’t already mulched with shredded wood, apply a layer 5 inches thick in a circle 5 feet in diameter, and kept 5 inches away from the trunk. This moderates soil temperatures in winter, preventing extreme cold from penetrating so deeply into the soil.
- Wrap trunks to prevent sunscald, which causes elongated, sunken, dried or cracked areas of dead bark, usually on the south or southwest side of a tree. Just as a skier can get a sunburn as snow reflects winter sun, tree bark can heat, thaw and refreeze on sunny days, rupturing cells. Sunscald is especially damaging to young trees, smooth-barked trees and fruit trees. Older trees with deeply furrowed bark are less susceptible. Several forms of tree wrap and tree tubes are available at garden centers, and white reflects sun the best. If dark tubing is used, be sure there’s a dead-air space between the material and the trunk. Wrap trunks to the lowest branch, and slightly higher, if possible. Apply each fall and remove each spring.
- Wrapping trees is also a good way to prevent damage to the trunk from animals and rodents. Deer use young trees for rubbing posts, and rabbits and voles consume bark and branches. For best protection, bury the lower end of the tree wrap an inch or more below soil surface, which helps deter vole damage to the trunk at ground level.
- Unfortunately, wrapping the trunk doesn’t prevent all feeding injury, especially from rabbits, who use snowbanks for easy access to a tree’s upper branches. Younger fruit trees are attractive targets for rabbits, and the upper structure can be ruined by winter feeding. Prevent snowbank access with fencing placed around trees. Adding extra fence height might be needed in midwinter depending on the snow depth.
- Rodent baits or traps can minimize vole damage around trees and lawn. Where pets and children are present, baits can be placed inside PVC tubes, into which voles enjoy traveling.
- Although gardeners try a myriad of homemade repellents, including mothballs, human hair, soap and even vodka, all with mixed results, repellents with the widest researched success rate are those containing sulfurous compounds or blood waste, as found in Liquid Fence, Deer Away and Plantskydd.
- Water evergreens before the soil freezes solid, by soaking deeply. An amount that is sometimes used as a guide is 2 gallons of water for every inch of tree trunk diameter.
- Some evergreens, like arborvitae, are susceptible to winter sunscald and windburn damage. If protective burlap is used, instead of wrapping snuggly against the foliage, create a burlap screen around the evergreen with stakes inserted into the ground, creating a frame around which the burlap is wrapped.
- Arborvitae are particularly attractive to winter feeding from rabbits and deer. Protect with fencing or the repellents mentioned above.
- When using a snowblower, don’t aim it at trees or shrubs, especially evergreens. Many dead spots on evergreens are caused by the targeted force of blown snow.
Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at firstname.lastname@example.org.