Tips & Techniques to overwinter Perennials in Containers
I garden in zone 5, and do a great deal of perennial container gardening.. There are a number of great garden plants for containers including the hostas, heuchera, and ornamental grasses for shade. In sunnier spots, I love to mix and match different ground cover like Sedums and Delosperma. But by the time the killing frosts have knocked my perennials into dormancy, it is time to tuck away my favorite perennial pots for the winter to insure their welcomed return next spring.
Overwintering fact: Your overwintering success with container perennials is dependent on the ability to insulate the roots (containers). Plants grown in containers are exposed to colder temperatures than those grown in the ground, and are considered one zone colder. I live in Zone 5 which would make my pots rated a Zone 4.
How I've overwintered perennials in containers
I’ve gambled and left pots out all winter, and some made it, and some did not. So what do I need to do to make sure my potted perennials come back next year? I do recommend, (particularly in colder zones), to consider the following:
This is an old nurseryman’s technique for overwintering pots, and bare root plants. I dig a trench deep enough so my tallest container is level with the soil line. I group all my pots together in this trench and fill it in with the leaves I haven’t raked up yet. Burying your pots will help insulate the roots
No time to dig? You can group all of your pots tightly together and cover them with either a thick layer of leaves, or potting soil.
Knock ‘em over
Knock 'em over on their sides. Here, you are keeping your roots warmer by laying them down. You will still want to group them together, and ideally, cover them with leaves for some extra insulation. I find this is especially helpful with Hostas pots. I have lost potted Hostas not so much to the cold, but to late winter when the snow melts, and creates a freeze/thaw effect which kills new emerging eyes. Simply laying pots on their sides minimizes this problem.
Bring ‘em on in
You will want to bring inside anything grown in a ceramic pot, or it will truly go to pot next spring, cracking into hundreds of pieces. I have stored numerous containers against a wall in my garage (a cellar would work). The important thing to remember here is that plants do dry out, and you will need to give them a drink by January or February and monitor them thereafter.
You might have your own methods of overwintering that have worked for you. (Please drop us a line - we'd love to hear about it!)
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