Frost-Proof Planters: Which Pots Survive a Winter Outdoors

The pots that most reliably survive a winter outdoors are made of plastic, resin or fiberglass, metal, concrete or wood. Terra cotta, earthenware and ceramic are the ones that crack, because they soak up water and the water expands as it freezes. If you own pots in the second group, you can still keep them, but they need to be emptied, lifted off wet ground or moved into shelter. Here is how each material behaves and what to do about it.

Why Pots Crack in a Freeze

The mechanism is simple. Terra cotta, earthenware and ceramic soak up moisture. When that moisture freezes it expands, and the pot wall has nowhere to go. A garden-products maker, BioAdvanced, describes this as moisture that expands as it freezes and cracks the container, and says water that collects in a pot can do the same, especially at the rim. The University of Nevada, Reno Extension makes the same point from the other direction: earthenware, ceramic and terracotta planters can expand and crack in cold weather, and repeated freezing and thawing is hard on them.

That repeated cycle is the important part. A pot that sits through one hard freeze may survive. A pot that gets wet, freezes, thaws in a sunny afternoon and freezes again is more likely to fail. If your winters swing around the freezing point, treat porous pots as high risk.

Pot Materials and How They Handle Winter

The ratings above follow the two sources cited below. Treat them as a starting point, not a guarantee. Individual products differ, and a thin wall or a poor mold can fail whatever the material. If a maker says a planter is frost-proof or all-weather, look for care instructions on the same listing and read them.

Fabric grow bags are a separate category. They have no rigid wall to crack, so they follow different rules. Our grow bags versus containers comparison covers how they differ from rigid pots.

Roots Are the Other Problem

A pot that does not crack can still leave roots exposed. A plant growing in the ground is insulated by the surrounding soil. A plant in a pot is surrounded by air on every side. The Nevada Extension publication notes that metal and plastic withstand winter weather but offer little protection for plant roots, and recommends moving cold-hardy plants in small or thin-walled containers into an unheated garage so their roots do not get too cold. Less cold-hardy plants can go against a wall shared with the house, or indoors.

Whether a particular plant is hardy enough for a particular pot is a plant question, so check the plant's tag or your local extension office. This guide covers the container.

What to Do With Pots That Can Crack

Pick the most practical option from this list, in rough order of safety for the pot:

1. Empty and store. If the pot is not holding a plant, empty it before storing. Nevada Extension suggests dumping the soil on a tarp, mixing in compost, and keeping it in a wheeled trash can for spring. Many makers suggest storing empty pots upside down so they cannot collect water.
2. Move into shelter. An unheated garage or shed keeps rain and snow off, which is the main thing. A shed does not have to stay above freezing to protect a dry pot.
3. Group and shelter in place. If you cannot move them, Nevada Extension suggests grouping outdoor pots together, out of the wind and close to the house.
4. Lift off the ground. BioAdvanced says manufacturers often suggest setting containers on narrow boards or bricks so they are not sitting on cold, wet ground. Pot feet do the same job and are easier to line up.
5. Fill heavy pots that cannot move. The same page suggests filling heavy containers to the brim with soil or compost so water does not pool inside, with a layer of straw held in place by burlap on top for some gardeners.

Large pots are heavy and awkward to lift. A rolling caddy lets you slide a pot into the garage and out again without lifting it. Check the caddy's weight rating against the pot, the soil and the plant, since all three add up. The rating is on the listing; we do not quote one here.

Choosing a Planter That Can Stay Out

If you are tired of moving pots every autumn, buy for winter from the start. Use this checklist:

• Material. Resin, fiberglass, metal, concrete or wood, per the table above.
• Drainage holes. Water that cannot leave the pot will freeze in it. Check that holes are open and large enough, and lift the pot so they are not blocked by the ground.
• Reviews that mention winter. Search the buyer reviews for words like frost, freeze and split. A planter sold for year-round outdoor use should not have a trail of winter complaints.
• Care instructions. A maker that sells a planter for outdoor year-round use should say so and say what it expects of you.
• Size against the plant and the winter. A thin-walled pot gives roots less cover than a thick-walled one, and a larger pot is heavier to move, so plan for both.
• Return terms. Large planters are expensive to ship back. Read the seller's policy before you order.

A Quick Spring Check

When the thaw comes, look over every pot before you refill it. Check the rim and base for hairline cracks, make sure the drainage holes are still open, and look at the feet or boards you used to see whether they have sunk or rotted. A pot with a crack that has not yet opened up is easier to retire before it is full of soil and a plant than after.

For raised and in-ground alternatives that avoid the freeze-crack problem altogether, see our Raised Beds & Planters page. If you are overwintering perennials in containers, our perennial overwintering guide covers the plant side, and the container gardening guide gives the wider container-gardening picture.