In cold climates where frost and frozen ground is common throughout the winter you should consider protecting your most sensitive plants. Evergreen shrubs can be protected against winter burn by using burlap or an anti-desiccant as mentioned in the Transplanting lesson.
You should wait until late Fall when temperatures are consistently cold (below 40 degrees Fahrenheit) before protecting plants with burlap. With anti-desiccants you will need a day warmer than 50 degrees Fahrenheit so it will stick to the leaves. Your best bet is to apply the anti-desiccant before the average temperature gets below 50 degrees. Always follow the manufacturer’s guidelines on the product you purchase as a few types of plants should not be treated with anti-desiccants.
For perennial gardens spread a 3 or 4 inch layer of leaves or hay over the entire bed once the ground has frozen. This will retard the repeated freezing and thawing that can kill perennials. One other type of winter protection: in areas that receive heavy snowfall you can build wooden billboard houses over woody plants that may otherwise be crushed by the weight of snow. This can be especially useful under the drip edge of a roof, where heavy snow shedding occurs. You can also tie up shrubs with twine to keep heavy snow from damaging branches.