MANHATTAN, Kan. – Winter is hazardous for newly planted trees, even “mighty oak” saplings. Sometimes it remains dangerous for trees that stay fairly smooth and thin-barked as they grow -- including ashes, honeylocusts, lindens, maples, willows and most fruit trees.

The cold weather’s perils are twofold (although drought can add a third). Winter’s freeze-thaw cycles can cause sunscald and bark cracks. Foraging rabbits are able to be just as damaging, said Ward Upham, horticulturist with Kansas State University Research and Extension.

“In the central United States, many of the samplings will recover, if you provide some TLC later. But, the injury can still affect the tree’s strength and appearance for life,” he said. “Fortunately, you don’t have to take heroic measures to reduce the risk for either type of damage. Think of it as wrapping presents during October or November -- in time for Thanksgiving, perhaps.”

In most years, rabbit damage is likely to occur first, Upham said. The gnawing hoppers enjoy many fruit trees’ bark, but seem particularly fond of the tender tissues on newly planted trees and shrubs.

“That’s damaging enough. But, if they nibble all of the way around a trunk, it could die,” he warned.

The simplest barrier to rabbit damage is a 2-feet-tall, trunk-protecting cylinder of 1-inch wire mesh, chicken wire or the like, Upham said. Plastic tree wrap is another alternative, as is regularly sprayed liquid rabbit repellent on vulnerable plants.

Sunscald and bark cracks usually develop on the south or southwest side of trees, typically during late winter. To develop, they need warm winter days -- which research has found can heat sunward bark up to 40 degrees warmer than a tree’s shady side. This warmth can cause bark cells to break dormancy, lose cold hardiness. So, the active cells are susceptible to lethal freezing when temperatures drop at night.

“A bark crack can be a few inches long or be so bad it looks like a lightning strike,” Upham said. “Sunscalded bark becomes sunken and discolored in late spring and eventually cracks and sloughs off.

“But, to prevent that, you just apply tree wrap in fall from the ground to the start of the first branches.”

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