Terracotta pots in winter: why water in the saucer cracks them
The first frost often arrives overnight, and with it comes a risk for your favourite pots. Three small steps now lower the risk through winter considerably.
You planted your balcony with love over the summer, and the pots are still outside. Terracotta in particular absorbs moisture, and that is exactly what causes trouble in winter. A few minutes of effort go a long way towards preventing cracks and flaking.
Why terracotta cracks in frost
Terracotta is porous. It soaks up water like a sponge. When that water freezes inside the pot wall, it expands and chips off small pieces or splits the pot. It does not happen with every frost, but often enough that a little prevention pays off.
Standing water is especially risky: if the saucer is full, the pot freezes fast to it, and the base of the pot stays soaked through. That is where the first cracks tend to appear in frost.
Empty or remove the saucers
The simplest step: take the saucers off or tip the water out as soon as night frost is forecast. If you leave pots outside, put them on pot feet or small wooden blocks so excess water can drain away.
Also check that the drainage hole is clear. A blocked hole keeps water in the pot, and that is where it freezes.
Store empty pots dry
Pots without plants are best stored dry and frost-free, for example in a cellar, garage or shed. Brush them off first so soil residue and pathogens do not carry over into next year. When stacking pots, put a little paper between them so nothing sticks together or chips.
Empty pots that have to stay outside go close to the house wall, tilted slightly so no rain collects inside.
Planted pots: protect the roots
Hardy plants such as lavender, thyme or sage usually cope well with the cold in the ground. In a pot, though, the roots are much less protected, especially in harsh regions such as upland areas or the Alpine foothills. Wrap the pot in hessian, bubble wrap or coconut matting and stand it on wood or polystyrene so the cold does not creep in from below.
Water only on frost-free days, and sparingly. In winter, waterlogging often harms plants more than the cold itself.
Frost-proof alternatives
If you would rather not haul pots around every year, choose glazed stoneware, plastic or metal. Dense stoneware absorbs hardly any water and is far sturdier. Terracotta varies too: pots labelled frost-resistant are fired better, but that is no guarantee.
In the Rootivo bed planner you can note down what grows where, which is handy when you set everything out again in spring.