Snow fell throughout the Cincinnati area on Thursday. This blanket of white will add insulation for plants as we head into the deep freeze, not to mention some much needed moisture.
The combination of cold ground and bare soil can be hard on plant roots. Roots are generally only hardy to 25 degrees Fahrenheit. If soil temperatures fall below this level, roots can be injured. Plants such as 'Knockout' roses have shown themselves to be particularly susceptible to such damage. Herbaceous perennials can be subject to frost heaving and damage when soils are bare.
Mulch helps to mitigate soil temperature fluctuation. Snow does an even better job. Snow is a wonderful insulator. Snow crystals contain a lot of air, and this air content provides great protection against fluctuations in temperature.
A number of years ago, we had a warm winter early and late, with six weeks of cold and snow in the middle. A warm December left soils relatively warm and lawns green. Snow and cold struck in January and temperatures bottomed out at -20 F. Despite this intense cold, when warm air flooded back in mid-February, the melting snow revealed green grass, The soil had never frozen under the blanket of white.
Plants in above ground planters or pots can be particularly vulnerable to freeze injury in winter. The sides of the planter are as exposed to the cold as the top surface and cold penetrates from all sides. If possible, move planters into an unheated garage in winter or false plant them in the ground.
When snow melts, the moisture slowly seeps into the soil, providing a nice moisture supply for plant roots Liquid precipitation (including melted snow) has been well short of normal over the past two months. While the moisture content of this snow is rather low, every little bit helps. Lack of moisture can cause desiccation injury to some plants, especially evergreens. It can even be good to water evergreens occasionally in winter, especially if they are near foundations or building overhangs.
Snow can cause some problems for plants. Heavy snow loads can break branches, rodents such as voles can tunnel under snow and feed on tree bark, and de-icing salts can also cause problems. However, even with the problems, it is important to remember the many benefits of snow.
Snow can wreak havoc in an urban area. However, it is nature's way of placing a blanket over trees and shrubs. Do your best to stay off the roads so you can enjoy the beauty of the winter wonderland. And remember, your plants are happy!