This recent snowfall and record-shattering temperatures are impossible to ignore. Can you imagine being a plant out in these conditions with your roots in wet, frozen ground, covered in snow, and exposed to brutal winds?
What's a plant to do? There is good news. Snow is an incredible insulator. Things like perennials and shrubs that are buried under snow are better off than tender stems that are above the snow-line exposed to the full force of below-zero temperatures and wind. Also, plants recognize real air temperature, not wind chill.
As mentioned, snow is beneficial. The best case scenario for plants in the winter is for temperatures to be in the upper 20s/low 30s, allowing snow cover to remain until late winter. It's the alternating freeze/thaw, warm/cold, warm/cold cycles that really damage plants. Which is unfortunately what is most common here in the Chicago area.
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 - try to direct the top of the chute so you're throwing snow beyond the plants to best protect them.
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.
One common question we get a lot is: "Should we remove snow and ice from branches?" It's a great two part question.
1. If you see evergreen branches weighted down with SNOW and you can gently shake it off without breaking that's great! Use something soft like gloved hands or a broom that doesn't have hard parts to physically damage the plant.
2. 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 also 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!
Chief Horticulture Officer