Recent snowfall and record-shattering temperatures are impossible to ignore. Can you imagine being a plant out in those conditions 24/7 with your roots in wet, frozen ground, snow knee high, and the rest of your "body" exposed to brutal winds? It certainly goes beyond my definition of chilling.
What's a plant to do? There is good news. Snow is an incredible insulator. So, things like perennials and shrubs that are buried under snow are really safer than tender stems that are above the snowline exposed to the full force of below-zero temperatures and wind. Further, plants recognize real air temperature, not wind chill.
The latest USDA plant hardiness map shows the area adjacent to Lake Michigan as Zone 6 (minimum low -5/10 degrees F.). The temperatures our landscape plants have just experienced are Zone 5 minimums (-15/20 degrees F.). So, those of us that push the hardiness boundaries with Zone 6 plants may get our garden comeuppance this spring. I should check my black suit as I may be holding spring services in my own garden. Oh well, we plant die-hards (haha) say you really haven't tried a plant until you've killed it three times!
Sorry, I digressed. Again, snow is beneficial. The best thing that could happen for the rest of the winter is that temperatures would rise to the upper 20s/low 30s, allowing snow cover to remain until late winter. It's alternating freeze/thaw, warm/cold, warm/cold cycles that really damage plants.
The logical question that arises from that statement is, "So, it's alright to bury them in snow?" Yes, with a big caution about how the snow is placed on them. Perennials are kind of a nonissue since they're largely cut back. There's not much of consequence to damage. For things you left standing, like ornamental grasses, it's not the end of the world if their foliage is bent over and broken.
On the contrary, flowering shrubs and evergreens that have slender, breakable stems shouldn't have shovelfuls of heavy, wet snow dumped over the top. If the snow is light and fluffy, and can be placed gently around plants, that's fine. For those that use snowblowers - If you can direct the top of the chute so you're throwing snow beyond the plants, that's great.
Ice encasing plants is very different than snow. Not only do you have more potential for physically breaking branches, but there is a likelihood of plant parts dying from being encased in ice for long periods of time, particularly evergreens. Preventing these stalactites from reaching the plant and encasing it may prevent a lot of branch amputation come spring.
If the plant is encased in ice you can only hope for a gradual melt. Don't be tempted to use a bucket of hot water as a deicer. Don't laugh. Anything that can be conceived can be done... and has been. The results aren't good.With ice, you just have to wait and see what happens in the spring.
With plants buried in snow, damage can come from deer and rabbit grazing. With little leafy and green in the winter landscape certain evergreens must be looking mighty tasty. At this stage I would recommend draping valuable plantings of arborvitae and yews with black mesh netting (appropriately called "deer netting"), pegging it down with bricks or stones. That should reduce animal browsing.
Pay attention to the deicing products you use on surfaces. Avoid salt-based products which can damage plants either by splashing on foliage, or being absorbed through roots later. We recommend products like Paw Thaw (calcium magnesium acetate) that decompose into by-products that are safe for plants and pets, while not having negative effects on soil.
Here's hoping the spring thaw brings you a garden unfazed by winter weather!