Earthy, orange terra cotta pots are a quintessential symbol of gardening. They also inspire a love/hate relationship with gardeners, due to their penchant for cracking. With sub-freezing temperatures creeping their way into the Chicagoland forecast, it’s a good idea to prep those containers now for a long winter nap. Wait too long, and you’ll most likely have a collection of broken pots come springtime.
Aside from it’s aesthetic appeal, why would we want to use terra cotta instead of something supposedly more durable? The answer lies in a combination of qualities that offer advantages over other materials. Terra cotta is made of fired clay, a natural resource. It’s slower to heat up and cool down than wood or plastic, resulting in less temperature-related stress to plant roots. Terra cotta is also porous and ‘breathes,’ allowing air to circulate inside and out (yes, roots need air circulation too). It’s this porous nature that also allows water to pass through the material. That’s a good thing, making over-watering nearly impossible.
However, the porous nature of terra cotta creates problems for us in cold weather. Water soaking through a clay pot becomes frozen when temperatures drop. As water freezes, it expands in volume and subjects the container to pressure. When the temperatures then rise above freezing again, any ice trapped in terra cotta then melts, leaving larger spaces for more water to enter and potentially freeze again. This cycle of freezing and thawing, with it’s expansion and contraction, results in cracking. Even one good freeze can be fatal to terra cotta if enough moisture is present.
If you like the idea of keeping your terra cotta pots for many years, there are a few tips to help them survive winter:
Soil retains moisture, so your first line of defense in winterizing terra cotta containers is to empty them entirely. That means not only removing dead plants and dumping out potting soil, but also scraping out the little bits and pieces of growing medium that stick to the inside and bottom. Pot scrubbers designed for kitchen use work great on terra cotta, as do hard brushes or even soft steel wool.
Fungus, bacteria and viruses can survive the winter inside your emptied pots, and it’s a good idea to clean containers thoroughly after they’ve been emptied. A common method is to wash them with a solution of 90 percent water and 10 percent bleach. They can be soaked in the solution or washed by hand, but in either case, be sure to let the solution sit and do it’s work for 30 minutes before rinsing them off with water.
If you can bring your terra cotta containers somewhere indoors where they will be warm and safe from winter weather, then your task is complete. If not, even an unheated garage or storage shed will protect them from temperature extremes related to sun and exposure.
If your only option is to store containers outdoors, you’ll want to make sure they are off the ground and away from freezing/thawing moisture. There are commercially available ‘feet’ that act as risers, and they’re made of terra cotta to match the color of your pots. Bricks or blocks of wood work just as well. You’ll want to cover up the containers to keep rain and snow off them. And make sure the drain holes in the bottom are not obstructed in any way. There’s no guarantees though – storing terra cotta outdoors is a game of chance.
PICK UP THE PIECES:
If your pots do happen to break over the winter… all is not lost. Many gardeners use the broken shards as drainage in the bottom of new pots.