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Knowledge to Grow by Purdue Master Gardener Karen Weiland - Overwintering perennials in containers

I awoke this morning nestled beneath my warm blanket and began to think about what I was going to write about for this week’s gardening article. Then it came to me – my warm blanket protecting me from the cold air could be compared to the blanket of snow that protects perennials during the winter months.

Snow in the winter is what woodchips are to the summer….think protective mulch. When I am removing snow from the walkway I always try to place it on a bare area containing perennials.

Snow can act as an insulating barrier for perennials in containers as the freezing weather can damage roots in thin pots. I like to group my potted perennials together along an area of my house and then keep them covered in snow as it is available. You can also cut off the boughs of a Christmas tree and lay them on top of and around the potted perennials to give them extra protection. Avoid placing the pots on a raised location such as a deck as the exposure to the cold air from below can be detrimental.

During late fall, before the ground has frozen, potted perennials can be placed into holes dug in the ground. The soil acts as an insulator to protect the roots. Just remember to remove them in the early spring. If left in too long, the roots can begin to grow so much that they will grow through the drainage holes and anchor themselves to the ground. I have placed pots in a wind-protected area, turned them upside down to keep the pots from cracking, then covered them with a combination of mulch, leaves and pine boughs with much success. Once the weather has warmed, I start checking my overturned pots for signs of growth.

Potted perennials can also be stored in a garage or outbuilding, however it has to be a cool location or they will not overwinter properly. Always keep in mind that the tissues of some plants – especially trees and shrubs – are more susceptible to cold weather damage in their youth or the first couple of years after transplantation. It is only when they have reached a certain level of maturity that they are then fully hardy.

Until next time, Happy Gardening!

The Purdue Cooperative Extension Service can be reached at 499-6334 in LaGrange County.