A Broken Pot Pressed Back Into Service
A Broken Pot Pressed Back Into Service

Sometimes it seems like winter is harder on pots than on plants.

If you have  pots – especially terra cotta pots – in your garden, you probably lose a few every winter.

Is there any thing you can do to protect them? Of course! But first, you need to understand why pots break. As with so many things in a Northwest garden, it’s not the temperature alone that’s the culprit – it’s the moisture.

Pots crack in the winter for one of two reasons:

  1. Terra cotta is highly porous. It absorbs and holds water, sometimes going weeks without drying out. When temperatures drop, this water freezes. As it freezes, it expands. The ice forming inside the clay eventually breaks the pot.
  2. Soil in a poorly drained pot becomes sodden. As the temperature falls, the water in the soil freezes. This causes the volume of material (soil, roots, and ice) to expand. Under pressure, the pot cracks.


What can you do to protect your containers (and the sometimes large investment you’ve made in them)?

Unglazed terra cotta pots are most at risk for winter damage. Clay is highly absorbant and very brittle. Traditional clay flower pots are almost guaranteed to chip, crack, and break during a Northwest winter. To protect them, move the pots into an unheated garage or shed, or even under a deck out of the rain.

If the pots held annuals, and you plan to replant with new flowers in the spring, empty all the soil, and disinfect the pots with a mild bleach solution before storing them. Stack the pots upside down in a dry area for the winter.

Terra cotta pots that have been glazed only on the outside are as much at risk as their unglazed cousins. The glazing is mainly decorative. It does not protect the pot from the elements. Water is still trapped by the clay, with the same unfortunate outcome: cracked and chipped pottery after a hard freeze.

Containers that have been glazed inside and out have a better chance of surviving the winter – but the odds are still against it. Moisture can still build up in the soil or even through the bottom of the container (which is rarely glazed).

If you have decorative terra cotta containers and you want to be sure they make it through the winter – don’t leave them unprotected outside.

Concrete, plastic, and fiberglass containers are much sturdier than clay. They don’t attract moisture, and rarely experience frost or cold damage in the Northwest. New styles and colors make some of these pots – especially the fiberglass ones – every bit as attractive as traditional clay pots.

Don’t fight nature. If you want to leave your pots planted year round, avoid terra cotta.

This post was Part 3 of a series.
Part 1: Caring For Your Winter Garden
Part 2: Frozen Ground

Photo by A. Davey Released under Creative Commons License