To keep your young tree healthy through the winter there are several maintenance tips to keep in mind. You need to protect them from mice and voles gnawing around the base of the tree because they can easily girdle the bark and cause a tree to die. A simple way to prevent this is to use a plastic wrap. Simply put it around the base of the tree about an inch or so below the soil line and wrap it around the tree all the way up. This will prevent the little mice teeth from gnawing on the bark. Another thing to remember in winter is that the south side of the bark may heat up during the day, then when cold temperatures come at night it causes the bark to split. To prevent that splitting or sun scald you can take some nylon tree wrap, wrap it around the tree, tie it at the bottom and the top and the white color will reflect the sunlight so it doesn't heat up so much during the day and the bark doesn't split. By using both these techniques you can help your young trees turn into healthy old trees.