5 Easy Tips for Protecting Your Potted Plants This Winter
Unlike annuals, perennials and shrubs don’t die in the winter, which leaves many gardeners wondering, “how do I overwinter my perennials and shrubs in containers?” It’s a good question to ask, too! Overwintering plants in containers is quite different from overwintering them in the ground – all thanks to their roots.
In winter, the soil stays warmer than the air, protecting roots from cold winter temperatures. However, when you grow perennials and shrubs in pots, they lose the extra insulation that soil provides. Instead, containers freeze and thaw quickly, which is especially stressful (or even deadly) for your plants.
With that being said, not all plants will perform poorly in winter containers. The rule of thumb is that plants are winter hardy in containers if it is two zones hardier than the zone you live in. Great Garden Plants is located in zone 6, which means we can grow plants hardy to zones 4 and lower without problem in containers. We always recommend growing plants that are two zones hardier for success. But don’t let this rule stop you! If you’re determined to grow plants that are hardy to your zone (or just one zone hardier), there are some extra steps you should take to make sure they survive.
We’ll walk you through our 5 tips for overwintering your plants in pots this winter:
Pick the Proper Pots
What’s the worst thing that could happen to your containers over winter? They crack – or even worse – they completely shatter. Clay, ceramic, concrete, or glazed pots are all susceptible to cracking when left out in freezing temperatures. There are two reasons why you want to avoid this. First, you may lose your favorite decorative container. Second, large cracks will further expose the plant’s root system to freezing temperatures and winter winds. The roots are likely to dry out, which puts your plants at risk of death.
We also don’t recommend leaving any perennial or shrubs in the plastic nursery pots they arrive in over winter. Because they are so thin, they provide little to no insulation for the roots, leaving them exposed to cold temperatures. They are likely to freeze and thaw periodically, which is traumatic for the plant.
Instead, we recommend overwintering your plants in plastic, wood, or composite pots that can withstand freeze and thaw action.
Move Your Planters
It can be a gamble to leave your plants as-is on your patio for the winter. Instead, we recommend moving your planters to a sheltered location that’s protected from winter winds. Either next to your home or shed, under your deck, or even in an unheated garage. It will save your pots from the freeze and thaw cycle, prevent root damage, and protect branches from breaking in strong winds or ice. Evergreen shrubs and perennials will still require bright light, but dormant plants can handle darker areas for winter.
We never recommend bringing your pots into a heated space (like indoors). Why? Most perennials and shrubs require a dormancy or chill period to grow and flower the following season. They expect, and actually hope, to undergo cold winter temperatures. Completely skipping a winter season may stress them out to the point of death.
*If moving into a shed or garage, wait to do so until winter temperatures drop well below freezing and the plant is almost in full dormancy.
If you can’t move your containers to shelter, you’ll have to bring to shelter to your containers! Try wrapping your pots with insulation, like blankets, burlap, or thick bubble wrap. This protects your pots from cracking – but more importantly – it protects the roots from harsh freezes that can damage the plant.
Don’t mind the extra work? You can always use nature’s protection: the soil. Dig a trench and bury the potted containers up to the base of the plant. This will provide as much insulation as it would have if planted in the ground.
No matter which option you choose, make sure you finish by insulating your plants with a layer of mulch. This ensures the soil stays moist and a little warmer
Surprised you still need to water your plants in winter? Dormant does not mean dead, so your plants still need water! Roots may die from desiccation in dry pots, so it’s important to keep them moist throughout the winter. This generally isn’t a problem if your plant isn’t sheltered from winter precipitation. However, if you moved your pots under a covering, they shouldn’t be ignored.
When we say moist, we do not mean soaking wet. It’s important to water your plants infrequently and with a light hand. Check on your plant every few weeks or each month, feeling the soil with your fingers to get a sense of how wet it is. If the soil feels moist, skip watering. If it’s drying out, consider lightly watering again.
Avoid Fertilizing & Pruning
It’s natural for plant growth to slow down (or stop completely) in fall and winter for a good reason. Leafy new growth and soft stems are not tolerant of cold temperatures. They’re the first part of the plant to die once freezing temperatures hit. What does this have to do with fertilizing and pruning?
Both fertilizing and pruning encourage the development of new growth on plants (particularly, shrubs). Do not apply fertilizer after midsummer to allow your plant to naturally enter dormancy. If you’re planning on pruning or cutting back your plants, do so in early spring.