When winter arrives, life slows down – critters hibernate, and plants go dormant. While you don’t have to worry about wildlife creatures, your potted plants may need overwintering care. You may even ask, is it alright to leave your soil-filled pots outside in the cold?
As a general rule, never leave pots filled with soil out in winter. Terracotta and ceramic pots will crack because the soil will expand as it freezes in the cold. Wooden, plastic, metal, and fabric planters may last longer. However, these will eventually suffer from discoloration and bursting seams.
Oh and just in case you want to know how you can grow your veggies in the winter while you’re at it, check out our article: How to Grow a Food Garden in the Winter
Below, I explain further about these various containers along with helpful tips to overwinter them:
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What Type of Pots Should Never Be Left Outside in Winter?
Clay-based pots such as terracotta and ceramic should never be left outside during winter. Their solid structure is just not malleable enough to handle the soil’s expansion, cracking instantly in cold weather.
Additionally, terracotta pots are porous. Any moisture left within its unglazed structure will break it apart. On the other hand, ceramic pots are glazed to prevent water loss. But if there’s so much as a chip on its coating, it’ll crack once water seeps in and freezes.
Either way, you need to care for these pots once winter comes. Here are a few tips on how to overwinter them:
- Remove all contents and clean them thoroughly. You can’t take any chances with leftover soil if you want to preserve them. Also, ensure to dry the pots thoroughly before storing them upside down indoors.
- Store them in an unheated basement or garage where the temperature is above freezing point. Even without the soil, you still want to avoid cold areas that could trigger a freeze-thaw cycle. Keep them cool but not chilly.
- Wrap layers of burlap or horticulture fleece (Amazon links) around the pot for insulation. This alternative is good if you have potted cold-hardy perennials. Not only are you protecting the pot, but you are also retaining heat for the plant’s roots. You can also group them with other plants and place them closer to your house, in the shade. Note: this applies to all pot types left outside in the winter.
Can large ceramic pots survive outside in winter?
It’s inadvisable to leave ceramic pots outside in winter as these will crack. Get rid of the soil and store the pot indoors, away from the cold. But if you can’t easily move them, wrap burlap around the planters and place mulch on the topsoil to retain as much heat as possible.
If you accidentally left your plant outside in cold temperatures too check out our article: How to Best Warm Up a Plant Exposed to Cold Temperatures
And if your plants got hit by frost and you are wondering what to do about it, read this article: Can You Really Wash Frost Off Plants? – With Alternatives
What Pots Will Be Safe When Left Outside In Winter?
There are five types of containers that you can safely leave outside in winter:
However, this doesn’t mean that they are indestructible. Eventually, these planters will suffer damage. But with proper care, you can make them last as long as possible.
Here are a few tips on how to take care of them:
- Empty 1/2 or more of the soil from the containers. Except for fabric planters, repeated soil expansion will eventually cause the pots to burst from their seams, like wood, or crack like plastic and concrete. This trick helps prevent that every time the potting mix freezes.
- Keep plastic pots away from direct sun exposure. Otherwise, this will discolor the planter and weaken its structure in the long run.
- Line wooden planters with landscape fabric to prevent soil moisture from rotting them. All wood will eventually rot, but this hack can extend it a while longer. Opt to get quality non-treated wood such as cedar or redwood if you can. They’re a bit on the pricier side but worth the investment.
- Remove plant saucers to prevent standing water from freezing. Use pot risers or pot feet (Amazon link) instead to elevate your plants instead.
- Don’t drag fabric grow bags (Amazon link) across the ground to prevent tearing. It’s better to carry them instead to avoid any scraping to the bottom of the bags. Otherwise, they won’t last as long. They are arguably the best planters to overwinter in your garden because they easily accommodate soil expansion with no problem.
However, you’ll still need to wrap outdoor potted plants in a protective covering to keep the roots warm if they’re perennials. The plant may be dormant, but not the roots. They will be affected by cold damage if you don’t insulate them well enough. For more information on protecting your potted outdoor plant, you can read all about it in this article.
Can You Leave Soil In Pots Over Winter?
It’s alright to keep potting soil in planters over winter, provided it is dry and the pot will survive the harsh season. It doesn’t matter whether it came from an annual plant or still has a perennial in the soil; it’s still viable. However, it’s worth noting that you’ll need to clean and revitalize the soil with fertilizer once spring comes. Dumping the soil out will also make it easy to check whether any insects or critters took shelter in it over the winter.
Here are a few tips for reusing overwintered potting soil:
- Use a sieve to separate leftover roots and twigs from the previous plant. You want to make sure the potting medium is as sterile as possible. Over time, these plant remnants could rot, and you don’t want the resulting bacteria to infect your new plant.
- Add new soil, compost, or fertilizers to replenish nutrients. Potting mix doesn’t have the benefit of garden soil with live microbes and a constant flow of nutrients, so you’ll have to be the one providing the bulk of it. However, take care to do this in moderation. It’s better to first give less than the recommended dose to gauge how your plant will react to the new mix and adjust from there.
Do not reuse potting soil that had an infected/infested plant before. There’s nothing much you can do here other than discard it. It’s really not worth risking your new plant’s health when you can just get a new potting mix.
Overall, your pots are in more danger than your soil in winter. So hopefully, this article can help you steer away from that eventual mishap and save your beloved pots. Happy planting!