6 Smart Ways to Winter-Proof Your Outdoor Planters

For gardeners in frost-prone areas, finding a favorite pot that has cracked open over the winter and left cherished plants exposed to the elements is all too familiar. Without protection, many types of containers can be damaged by freezing weather. And if you're overwintering plants in those pots, it can bring a disappointing end to months of careful gardening. Here's how to protect your outdoor containers from cracking and breaking through the winter.

How Pots Freeze and Break

In temperatures below 32°F, the water in the potted soil freezes and expands, which can cause the pot to break. How soon the soil freezes varies based on several conditions. 

Plants growing in garden beds or in the landscape have a lot more leeway, as the surrounding soil provides expansion room. The soil also offers built-in insulation. In contrast, containerized plants are much more vulnerable to winter conditions, making proper protection crucial.

The size of the pot matters because the more soil around the plants, the more moisture they hold. Also, the sides of pots that touch the roots freeze quickly.

Types of Containers

Let’s look at the types of pots and how they respond to frost and precipitation. Overall, wood and frost-proof ceramics provide the greatest insulation, while clay and metal need the most protection. No matter the material, elevating containers off the ground with pot feet or a stand helps prevent freeze damage and improves drainage, giving your plants a better chance to survive winter.

Unglazed Clay (Terra-Cotta)

Because it is highly porous, terra-cotta absorbs water from the soil and precipitation, leading to cracking in freezing conditions when the water expands. These pots provide little insulation to roots.

Protection: Move indoors or into a sheltered area. Wrap with bubble wrap, burlap, or pack in straw. 

Standard Glazed Ceramic

The material absorbs some water. It is vulnerable to cracking if the soil freezes, so it provides modest insulation.

Protection: Move indoors if possible or wrap with insulating material. Ensure soil drains well to reduce freeze damage.

Frost-Proof Glazed Ceramic

Fired at high temperatures, these materials are dense and non-porous. They resist cracking from frozen soil yet offer moderate insulation to roots.

Protection: Can usually remain outdoors safely if elevated. Protect in extreme cold.

Resin/Fiberglass/Plastic

Non-porous and very frost-resistant, these materials have minimal cracking risk. The soil may still freeze, but the pots retain warmth slightly better than clay.

Protection: Generally safe outdoors if elevated. 

Metal

Pots made of metal conduct heat and cold quickly, so roots of any plants in them are rapidly exposed to freezing temperatures. These containers create temperature shocks with sun exposure, followed by frost.

Protection: To protect roots, wrap the outside with frost cloth or burlap or line the interior with a pot liner. Make sure drainage holes remain clear.

Wood

Moderately insulating due to its thickness, wood is slower to freeze than clay or metal. Prolonged wet conditions can damage roots.

Protection: Best elevated; keep drainage holes clear. Apply wood preservative if desired.

Ways to Protect Pots

Help all your pots and planters get through winter damage-free with these simple tips.

1. Relocate the Most Vulnerable

Small pots are the most prone to freezing the roots of your plants. Certain plants, like dahlias, lavender, and coneflowers, are prone to rotting in cool, wet conditions and should be protected from consistent rain and snow. Move smaller or tender plant pots indoors, under an eave, or to a protected porch. 

Grouping pots near sunny walls adds extra warmth from reflected heat. To move heavy planters, use wheeled pot caddies, dollies, or strapped “pot lifters."

2. Elevate Pots

Contact with the ground conducts cold temperatures. Place pots on bricks, wooden blocks, or pot feet to allow drainage and prevent freeze damage.

3. Drain and Reduce Soil Moisture

Remove excess water from saucers and soil, especially in self-watering containers, to prevent expansion.

4. Wrap or Insulate Pots

When a pot is too big to move, wrap it for extra insulation. Breathable burlap or frost cloth is best to promote the circulation of air and moisture. Bubble wrap traps and repels water, so only wrap the pot (not the plant), and ensure drainage holes are open.

5. Boost Warmth Around Pots

Surround pots with bricks, large stones, or sealed milk jugs filled with water that will hold the sun’s heat and radiate it at night.

6. Mulch

For extra protection, add a layer of mulch, straw, or shredded leaves on top of the soil. This helps insulate roots and reduce temperature swings, no matter the pot material. Top dress with wood chips to add nutrients and retain moisture, or use gravel as a winter mulch for plants that prefer drier soil.

Winter Care Tips

Replacing pots is expensive, and losing plants can be heartbreaking. With a little attention before winter sets in, you give your potted plants the best start for a long and cozy winter.

• It’s important to check the soil moisture of your pots periodically. Deep watering before frost is in the forecast helps your plants recover faster. Don’t overdo it, however; you don’t want the soil waterlogged.
• Remove heavy snow or ice accumulation from the plants and the pots.
• Inspect pots for cracks and repair minor damage if possible.