Winter can be a tough time for landscape trees. Fortunately, there are things you can do to keep your trees healthy.
The trunk of a tree can be at risk in winter. Young trees and those with thin bark are the most at risk. Sunscald is one problem, which occurs on sunny, below freezing days. The sap warms up in the sun, but then it quickly refreezes and expands. This damages the tree. Deer and other hungry animals in winter may also browse the bark and cambium layers on trees, causing chewing damage.
Tree guards are plastic tubes that slot around the trunk. The guard you choose must be larger than the trunk so that it doesn't cause constriction in the event the tree begins to grow before you remove the guard. Typically, the guards are removed each spring, unless wildlife browsing is a major concern.
In some areas high winds area normal part of the winter weather patterns. Young trees are most susceptible to wind damage simply because they don't have extensive anchoring trees, but some older trees can also be at risk. A tree service can provide guidance on which trees to stake.
Generally, you only need one stake since you do want the trunk to sway slightly in the wind -- that is how the tree develops strong roots. The stake should be set several feet out from the trunk and it must be about as tall as the trunk from the ground to just below the first lateral branch. When attaching a support line, it must run parallel to the ground and about three feet above ground. Older unsteady trees may require more in depth staking, so check with a tree service first.
Evergreen trees, particularly of the needle variety, can suffer an issue called desiccation. This is when a combination of winter wind, extreme cold, and lack of soil moisture causes the evergreen needles to dry up and fall off. Broadleaf evergreens can also suffer from desiccation, but it isn't as common.
Burlap is a dependable protection against wind damage and desiccation. The burlap is wrapped around the tree snugly, but the top is left open so that air can circulate and excess moisture can evaporate. Twine is then used to secure the burlap in place. The burlap wrap must be removed before active growth resumes in late winter.
Contact a tree service in your area, like http://www.prtree.com, to see if your landscape trees can benefit from some extra winter protection.