Surviving Winter

February 7, 2019

It’s cold outside today…like, really cold. And while our solution to keeping safe in these temperatures is simply not to engage, our plants just don’t have that option. From the cozy warmth of my insulated home, I gaze out at my perennial garden and think about the lush green plants that will begin to pop up in the spring. Year after year, they endure freezing temperatures and still manage to emerge in all their glory when the time is right.

Part of the joy of planting native perennials is knowing that they are cold hardy to our climate zone. In Illinois, our cold perennialhardiness zone is 6 for the northern part of the state and 5 for the southern half and the small area surrounding Lake Michigan. Native plants of our region have evolved to survive the harsh winters in these zones, but how exactly do they do that??

These marvelous perennials have adapted several techniques that help them survive these conditions. As days shorten and temperatures begin to gradually drop in the late summer and fall, plants receive these signals as notification to start preparing for winter. Trees drop their leaves and perennials die back to their root crowns. By losing their green leafy parts, plants halt photosynthesis and go dormant. This means they are no longer actively growing. As a result, they are not taking in extra water, which can quickly freeze and damage cells over winter.

In order to survive, however, plants do need to store some water in their cells during times of freezing temperatures. To prevent this storage water from freezing and rupturing cells, plants have developed another awesome technique. As part of their winter preparation, they actually alter the composition of this water solution. By adding sugars and salts to the water stored, they lower the temperatures at which the solution will freeze, protecting them from damage.

Nature helps plants out as well. Natural blankets blanketsdraped over the root systems, such as fallen leaves and snow, keep the roots warmer over winter. Not only do these blankets protect plants from harsh winds and keep soil temperatures far above the ambient air temperature, they also help the temperatures stay consistent, which further increases the effectiveness of the plants’ survival strategies.

With all of these amazing evolutionary tools, it’s easy to see how these plants survive. They are way better equipped than we are! But as we have all experienced, sometimes even the best prepared plants do not make it through our winters. Fluctuating temperatures can trick plants into dropping these defenses too early, causing cells to freeze and damage to occur. A lack of snowfall can leave plants exposed to harsh winds and allow soil temperatures to drop to dangerously low levels. And of course, desperate little critters in search of food will go straight for the roots and stems of our dormant plants. So, even with all of their own defenses, sometimes our perennials can use our help!

Here are a few techniques you can use to further increase the chances of your perennials surviving the winter:

  • Once plants are dormant, add a layer of leaf mulch or compost 6”-8” Mulchdeep in order to guarantee the blanket they need for the winter. This is especially important for the youngest plants in your garden!
  • Do not plant perennials too late in the season. Plants that do not have adequate time to develop before temperatures begin to drop will not have the full strength of all of their natural defense mechanisms to protect them
  • Stop watering plants once they have lost their leafy green parts. Excess water can cause rotting and freezing that can damage plants as the temperatures drop.
  • Install cages around those plants that seem to be crowd-favorites for animals in winter. This includes plants with underground storage systems, such as corms, bulbs and rhizomes, as well as small trees and shrubs.
Planting material out of season