Winter maintenance for trees

Hungry animals and the extreme weather of Minnesota winters are potential threats to young trees. The following includes a few tips to help prevent some of the damage that can occur in the winter months.

Sun Protection

For fruiting, flowering and thin barked trees (such as maples, honey locusts, basswoods and aspens) it is important to protect the trunks during winter months. Sun scald occurs when the sun heats up the bark to the point in which the tree's tissues are stimulated as they are in warmer seasons in order to grow. However, when the sun goes away, the temperature drops quickly and kills the active tissue. Use a light colored guard such as paper tree wrap or tree tubes. The trunks should be protected from the ground to the first branch. Install the guards in the fall and remove in the spring.

Sun scalded maple

Root Injury & Frost Heaving

Soil temperatures in winter are much higher than air temperatures. Tree roots cannot withstand as cold of temperatures as the rest of the tree. Sandy or dry soil (as in drought years such as this year) hold less heat so frost penetrates more deeply, which can damage the tree's roots. With newly planted trees there can be small spaces in the planting hole backfill that allow cold air to reach the root zone. New trees should be mulched with 6-8 inches of wood chips or straw to insulate the soil around the roots.

Additionally, freezing and thawing of the soil repeatedly in fall or spring causes the ground to expand and contract, which can damage new trees. Mulch is the solution to this problem as well, as it helps to maintain consistent soil temperatures.

Animal Damage

Hungry animals nibble on trees in winter and can cause severe damage. Wrap the trunk with mesh hardware cloth from 2-3 inches below the soil (for mice) to 18-24 inches above the anticipated snow line for rabbits.

Repellants should be used if deer are a problem.These make the tree smell or taste undesirable without harming the animal. Repellants can also be used against rodents.