Losing an established tree can be heartbreaking and also leave you with a gaping hole that's difficult to fill. It's good that you're thinking about this now, because, yes, there are things you can do to protect your trees from killing winter chills. Even in mild-winter Zones 7, 8, and 9, you can use these techniques when the forecasters predict below-freezing temperatures.
Water your trees and shrubs before winter. Trees don't shut down completely in winter. They can lose water through their branches and leaves, and when the soil is frozen, their shallow roots can't replenish the moisture. That's when dehydration sets in. Prevent this by watering trees well in fall and early winter-until the ground freezes.
Provide a sunblock. Winter sun and whipping winds can sap plants of their moisture. Shield young tree trunks from low-angled winter sun by wrapping the trunk with tree wrap. Wrap a tree trunk up to the first branch. Be sure to remove the wrap in spring.
Mulch much. If winter would stay consistently cold, plants would be happier. Temperature fluctua-tions throughout the season cause repeated freezing and thawing, which damages roots near the soil's surface. In spring, that damage slows growth and makes plants more vulnerable to disease. Insulate the ground out to the drip line with a 2-4-inch-deep layer of shredded bark or wood chips. And when you are shoveling snow, add a little extra around your trees and shrubs; a thick layer of snow also can act as mulch.