How to Overwinter Your Outdoor Plants
I’ve always loved container gardening. It’s a sign that spring has arrived when I get to use colorful annuals like coleus and petunias to create container “art” for my porch, points along garden walkways, and even for the vegetable garden.
But what about fall and winter? Is container gardening only limited to warm weather months? It doesn’t have to be. With a little preparation , you can get just as much pleasure out of designing and enjoying cool- and cold-weather containers.
Start by choosing the right container, and bigger is better. You want plenty of potting soil between the interior pot wall and your actual plant roots. This provides a layer of insulation for those tender roots when they’re above ground, exposed to the cold ambient air. You also want a pot that has drainage holes to allow water to escape so that your plants don’t become waterlogged.
Make sure your container is made of a durable, all-weather material like heavy or double-walled plastic, foam, fiberglass, metal, or wood. Containers made of ceramic, terra cotta, and concrete are at risk for cracking as water freezes and expands. I also don’t recommend gardening in winter with any heirloom or sentimental containers.
One clever way of adding a layer of protection to your containers – and their plants – is to wrap pots in bubble wrap or sheets of styrofoam. A few ways to get around this ingenious but tacky-looking solution is to layer the material inside the pot, or wrap the exterior of the pot with a decorative, seasonal material like burlap. If you leave the bubble wrap or styrofoam exposed, you are at risk of having your neighbors report you to the garden police – and I won’t bail you out!
Next, use a good quality potting soil – never garden soil. Potting soil is friable, providing the perfect growing medium and ensuring that plant roots don’t get soggy, a perfect path to disaster.
And most importantly, have fun selecting plants! For winter container gardening, I almost exclusively use perennial plants and shrubs. They can be beautiful and tough, and they provide me with plants I can either re-pot in the spring or move to my garden. The rule of thumb is to select plants that are two zones hardier than your current plant zone. For example, here in Little Rock I’m in zone 8a, so I’m well-served by selecting plants that are labeled for zone 6a or colder.
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A favorite combination of mine is to start with an evergreen like a pyramidal ‘Green Mountain’ boxwood (zone 4-9), and add coral bells like the yellow-leaved Heuchera ‘Citronelle’ or the stunning ‘Palace Purple’ (both zones 4-9). I like to work in some low-growing evergreen creeping phlox to fill in any spaces where potting soil is exposed, and top off the display with some yellow, purple, or rose-colored winter ice pansies (zone 7).
I also really appreciate the beauty of red twig dogwoods in winter container displays. The stark red branches are spectacular with a dusting of snow. Another shrub favorite of mine that also features red is winterberry holly (Ilex ‘Red Sprite’). I get to enjoy the ornamental red berries, and at some point in the winter, the birds will, too.
Other hardy perennials to consider using include perennial ornamental grasses, evergreen Christmas fern (Polystichum acrostichoides), variegated lilyturf (Liriope muscari ‘Variegata’), Pigsqueak (Bergenia ‘Bressingham Ruby’), and Dianthus ‘Firewitch.’
Evergreen trees and shrubs will benefit with the treatment of an anti-desiccant spray, which will prevent leaves and needles from drying out in the winter wind. During the holidays I like to fill containers with cut holly, magnolia and red berries from possumhaw (Ilex decidua.) The moist soil in containers helps keep the cut boughs hydrated.
Watering your containers in the winter is just as important as it is in warm weather. Don’t count on rain or snow to provide the pot with moisture. I check my winter containers once or twice a week and really drench them when they’re dry. I take a break from watering once the potting soil is frozen.
So in the coming weeks as I prepare to clean out my containers and compost what’s left of my summer annuals, I won’t feel any pangs that my container gardening season is over. I get to breathe new life into those displays for the coming winter months, and extend their beauty with year-round enjoyment – and you can, too.