Many of us like to push the limits a bit on plants we grow, hoping one that is not quite suited for our area will survive the winter. So we’ve usually got a few that aren’t as cold-hardy as they should be. As the winter nights get colder, these plants may be damaged or even killed. Even plants that are hardy can be damaged in a severe cold snap.
Plants suffer cold damage when they lose moisture from their leaves but can’t replace the moisture because the soil is dry or the water in the ground is frozen. Knowing and following a few basic principles will go a long way towards protecting your plants from winter damage and helping them leaf out again next spring.
The key is to make sure that the ground doesn’t freeze down to the root zone of sensitive plants. Moist soil holds and releases more heat than dry soil, creating a more humid environment around the plant when the cold pulls moisture from the foliage.
The best way to insulate the soil is with a 2-3″ layer of mulch. Place the mulch around the plant to at least a little past the drip line of each plant (the drip line is the outer edge of where water will fall when it drips from foliage). The mulch will allow moisture in but help prevent the ground from freezing down to the root zone. Snow on the ground (or on top of the mulch) will also provide some insulation-if you have snow on the ground, leave it right where it is!
Another way to protect plants is to stack or place pine needles, straw, hay or leaves around each plant. The first three are best, because they allow the plant to breathe-but in a temporary pinch, leaves will work. Simply start from the ground up and create a pile that covers the main branching structure to at least two feet above the ground.
Covering plants with frost cloth, burlap, or plastic will also protect plants an extra 2-6 degrees. The material should be secured over frames or stakes so that it does not touch the plant; otherwise, it will just transfer the cold. Make sure to remove these coverings during the daytime on any day when temperatures stay above freezing; this will allow the plants to absorb the warming sunlight.
When it snows, don’t rush out to brush all that snow off your plants. Believe it or not, a light layer of snow is actually good for perennials. Heavy wet snows can weigh down and break branches-but try not to remove lighter snow, as it is an excellent insulator against freezing temperatures that may injure plants. However, if it looks like you may get a partial melt, then a freeze, do remove it-ice is even worse than heavy wet snow.
Do not prune cold-sensitive plants until spring has arrived. In a sense, let the cold do the pruning for you. If your plant is injured, leave the damaged leaves on the plant to protect the foliage underneath. Premature trimming may stimulate tender new growth that could be damaged by a late cold snap. You may also end up cutting out more than is necessary, mistaking still-alive growth for dead. Prune only after new growth has started to appear.
If you have any questions as to which plants to protect, just ask one of our nursery professionals. We’ll help you make sure you’re ready to help your plants stand up to the cold of winter.