Spring, summer, and fall are all great times of the year to enjoy the great outdoors. It is when we can all enjoy being outside. But come winter, when we step outside on the coldest of days, we struggle to maintain a sense of feeling in our extremities, and wonder how anything could survive out in such frigid temperatures. Now, imagine you are a tree-you have made it through the warming spring temperatures, the heat of the summer, and the cooler temps that come in the fall months. But now, you are about to enter a battleground and attempt to remain alive through the harsh winter months as you stand there, unable to move to a warmer spot.
Winter brings heavy ice and snow loads, extremely bitter winds that increase water loss in evergreens, and a phenomenon known as frost cracking (where the thin bark of some trees has a sudden drop in temperature as the daily sun sets leaving the warmed bark now exposed to the frigid night temperatures). But the larger problem is that freezing temperatures can kill living cells within trees.
The number one goal of protecting a tree from freezing temperatures (and main problem caused by freezing temperatures) is a trees own ability to keep its living cells from freezing-a process that does not happen overnight (Snyder, 2012).
A tree's ability to protect itself during the winter months is actually a very complex process by which trees change the makeup of their cellular membranes, concentrate their sugars (forming a hypothetical anti-freeze) within living cells, and a process known as extracellular freezing (where the living cells force out their water into the spaces between themselves, thereby generating just the slightest amount of heat to keep the living cells alive).
Bark is also a form of protection from the frigid, exterior temperatures. Acting as an insulator, bark helps to keep the mass of wet of tissues found in the main stems a bit warmer, slowing the transfer rate between dry, cold outside air and moist, warm air found within the trunk (Coder, 2011).
A trees genetic capacity also plays a major role in determining a trees cold-hardiness and those species planted-but not fit to survive below a temperature threshold will ultimately lose their battle with the cold as determined roughly by our USDA Cold-Hardiness Map. While protecting a tree from the frigid temperatures is not a process that we can control, here again, starting with the right species for your site can lessen the effects caused by freezing temperatures here in Nashville, TN and the Middle Tennessee area. If your tree enters the winter months full of vigor and vitality, few stressors, no large wounds, and proper mulch protections above its root system, your tree will stand a much better chance of making it through to see another season.