Preparing Clay Pots for Winter Weather

By Janet (imapigeon) on September 18, 2010

One of the advantages of living here in California is year-round gardening. But in my area we still have occasional temperatures down to 18 degrees Farenheit, and several months of below-freezing temperatures at night. Many of my large planters contain perennials that need to stay in place year-round, and I've had to figure out ways to help both plants and pots survive winter conditions. Some of the things I've learned may help you, too!

When California's rains start, they can continue for weeks—and waterlogged soil can be disastrous even for vitrified1 containers.  Ice crystals expand as they form, and can exert enough force to crack container walls from inside.  Low-fired clay pots will absorb moisture from inside and out.  When water molecules freeze and thaw, these containers are then subjected to stress on both sides.

Unless you live in an area where it doesn’t freeze at all in the winter, unglazed red terra-cotta pots are probably best emptied, scrubbed out with soapy water, turned upside down and stored in a sheltered location.  Other low-fired containers---glazed or not---should also be emptied because even invisible chips or cracks in the glaze will allow the pot walls to absorb moisture.  All non-draining pots (such as those used for water features) should be emptied completely and protected so they can’t re-fill with water over the winter.

There’s a bit more flexibility with high-fired planters, assuming they have functional drainage holes and are planted with a fast-draining soil mix.  I mulch my large containers with rocks, which help retain warmth at night on the plant roots (and also keep the cats and squirrels out).  Before our freezing weather starts I check all my perennial planters to make sure they drain well, and add enouogh pebbles to bring the soil level up to the top of the pot wall.

None of my planters sit in shallow “drain dishes”, which I’ve found can actually prevent the pot from draining, allowing water to collect and freeze during the winter.  I think having containers up on pot feet is a better solution to the dreaded “pot ring” on my outdoor surfaces.

The daphne in this high-fired container is ready for freezing weather:

  • fast-draining soil will not become waterlogged
  • drainage hole has been checked to make sure it's not clogged 
  • container on pot feet will prevent the planter's base from standing in water
  • 2-inch layer of pebble mulch to the rim will help protect the plant's roots

2010-09-17/imapigeon/eaf60f

Winter weather can damage all types of clay pots in freezing temperatures.  Hopefully these tips will help you protect your favorite containers this year!

1Vitrify: “To convert into glass or a glassy substance by heat and fusion” (Webster).  Click here for an article on vitrification


Related articles:
container garden, planters, pots

About Janet
I've been involved with clay off and on since 1972----I love getting my hands in the mud! I've taken classes at several colleges, managed ceramic shops, and taught many students. After retiring in 2009 from environmental, health and safety, I began dedicating several hours a week to clay projects in my little studio. I especially like throwing planters, bowls and lidded jars, and I've made hundreds of handpainted tiles for my house. I do much of my firing at home, where I have both electric and gas kilns.

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Comments and discussion:
Subject Thread Starter Last Reply Replies
cracked pots glevely Apr 15, 2011 6:32 PM 9
Great article Janet valleylynn Nov 10, 2010 11:36 PM 6
Thanks LuvNature Sep 21, 2010 11:33 PM 1

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