Are you interested in keeping your favorite potted perennials and shrubs alive through the winter? There are a few important things to consider before the snow flies. Though the process isn’t foolproof, these six tips will improve your chances of success.
Tip #1: Select the Right Plants for Overwintering in Your Climate
The first factor to consider when deciding whether or not to try and overwinter a plant in a container is its level of cold tolerance. The general rule for a plant to be winter hardy in a pot is that it should be two zones hardier than the hardiness zone you live in.
For example, if you live in zone 6, choose plants that are hardy at least to zone 4. You might get lucky if the plant is just one zone hardier, but it is far more likely to survive the winter in a container if you stick with the two zone rule.
A pot of Reminiscent® Crema roses greet this homeowner all summer long with its fragrant, fluffy blossoms. This smaller statured rose is perfect for growing in containers.
Tip #2: Prep Your Plants in the Fall for Overwintering
Leave your potted perennials and shrubs outdoors where they will be exposed to cold temperatures and fall rains as long as possible until the plants go dormant. You’ll know they’ve gone to sleep for the winter when their leaves drop. Clean them out of the pot before they become mushy to avoid mold or fungal issues down the road.
One of the most important things you can do for your potted plants before winter is to make sure they take up as much water as possible before they go dormant. That’s especially critical for evergreen plants. Think of it like filling your car’s gas tank up before you take a long trip – your plants should be “full” of water before the soil freezes, or you store them away for winter.
What kind of container you are using to overwinter your plants in makes a big impact. The larger and thicker-walled the pot is, the better insulation it will offer your plants during the coldest months of the year. Larger pots that hold more soil have a greater buffer between the plant’s roots and the cold air. Overwintering success is often less in smaller containers.
As is true during the growing season, it’s also important that the container has a drainage hole for excess water to escape. Waterlogged soil – especially frigid cold, wet soil – is detrimental to plants while they are dormant. For that same reason, it is critical to use lightweight, well-drained potting soil whenever you are growing plants in containers.
The last factor to consider is the material the container is made from. If you plan to keep your potted perennials and shrubs outdoors for the winter, and you live in a cold climate, ceramic pots are not your best option. As the water in the clay expands and contracts during the winter, it can easily cause the pot to crack. Wood, metal, fiberglass and cement containers are better for overwintering hardy plants.
For a better chance at overwintering USDA zone 5 hardy, potted bigleaf hydrangeas in zones 5 or 6, consider following Tip #4 - providing extra insulation around the pot.
Tip #4: Insulate Extra-Sensitive Potted Plants
If you are worried about the container you are using to overwinter your plants, or if you have decided to push the limits of hardiness, consider insulating them before winter arrives. Wrap the pot in bubble wrap, burlap, foam insulation, old blankets or towels.
Overwintering several potted plants? Huddle them together in a group and they will protect one another from the elements. Go one step further if you overwinter your containers outdoors by covering them with a nice warm blanket of leaves or pine straw.
A protected spot up against a fence or a sheltered nook is a good place to overwinter your potted perennials. If you garden in heavy clay soil, your coral bells may overwinter better in containers where the soil is light and drainage is excellent.
Tip #5: Choose a Spot to Set Your Pots for the Winter
There are several good spots to set your potted perennials and shrubs for overwintering, but the one place you should not set them is inside your cozy, warm house. Many hardy plants actually need to be exposed to cold winter temperatures to grow and bloom well the following year. While you might not be a big fan of the cold, these plants are, so let them enjoy it!
Ideally, the perfect place to overwinter potted perennials and shrubs is outdoors, set up against your house, garage or fence. Choose a spot that is out of the wind but still exposed to the sun and precipitation. If your outdoor space is covered, you’ll need to water the plants occasionally through the winter. Keeping them out in the cold will help them stay in their natural rhythm.
If your plant is borderline hardy or your pot is ceramic, you’ll need to overwinter it in an unheated garage, shed, covered porch or cold basement. In these cases, a few extra degrees of warmth will protect the roots from freezing damage and prevent your pot from cracking.
Beware that mice are notorious for nesting in potted plants and eating their roots over the winter. Repellents or traps may be necessary to keep your plants safe.
Since Shadowland® hostas are very cold hardy all the way down to zone 3, they are typically easy to overwinter in containers. Once the foliage dies back, remove it to help eliminate pest issues.
Tip #6: Water in Winter, But Not Too Much
If you followed Tip #2, your plants will be heading into winter with a “full tank”. Keep it full by making sure the soil stays slightly moist through the winter months. Take care not to let the plants get waterlogged, but don’t let them dry out completely either.
This is easily accomplished with a few handfuls of snow set on top of the pots once every few weeks depending on the temperature. Sink your finger into the soil to test its moisture first. If you have a slew of relatively warm, sunny days in a row, the moisture will evaporate more quickly. No snow? Use a watering can instead.
Have you gotten this far and realized you don’t have the right conditions for overwintering your potted perennials or shrubs? No worries! Simply find a temporary place in your landscape to sink the plant – container and all – in the ground for the winter. That way, the soil in the pot will remain the same temperature as the ground. In the spring, pull the pot back out, clean it up, and you’re ready to go for the new season.
Contributor Bio: Susan Martin is an avid zone 6 gardener and content creator who enjoys spreading her passion for plants to others across North America.
All images courtesy of Proven Winners.
All articles are copyrighted and remain the property of the author.
By Natalie Carmolli for Proven Winners® ColorChoice® Shrubs
If you’ve ever been frustrated by hydrangeas that take forever to bloom-or worse don’t bloom at all-you’re not alone. But there is a variety that actually delivers on the promise of season-long blooms. To learn more Click here. .
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