Take care to store terra cotta pots during winter
Do I really need to move my new terra cotta containers inside for the winter? My gardening friends have advised me to put them in my garage during the cold months. — Sarah Jones, Barrington
Many gardeners use containers to add interest to their gardens and there are a few steps you can take to protect most terra cotta containers over winter. Terra cotta containers are popular and most of them are porous and absorb water that will freeze and thaw repeatedly through the winter and eventually cause the pots to crack if they are left outside. Seibert & Rice assures that its high-fired terra cotta pots — which are made of special ironand-calcium-rich clay from Impruneta, Italy — can remain outdoors even fully planted if properly elevated. If the containers are placed directly on the ground over winter, debris can block the drainage hole, which allows water to collect and freeze the pot to the ground. When the pot is moved the following spring, the bottom may fall off as if it had been cut off. The sides of the container can also crack, with the clay coming off in thin sheets.
The late fall freezes should not pose any problems for your terra cotta containers, so you can leave them out on display until hard frosts have completely killed the plants in them. Flowering kale can last well into November and still look nice. Start by emptying your containers. Remove dead vegetation, and if the plants that were in the pots did not have any disease problems, put the debris in your compost pile. If the plants were diseased, throw the vegetation and growing medium away, as most home compost piles do not generate enough heat to kill diseased organisms. Retain any growing medium that you’d like to keep in a plastic container or a bin and brush the pots clean as needed. Mix equal parts of the new growing medium with the old medium next year if you are reusing it. Scrub the pots with a solution of one part bleach to 10 parts water to disinfect them if necessary because of a disease problem. Once the pots are dry, they will be ready to put inside for the winter. I have had good luck storing my terra cotta containers in an unheated garage even with the growing medium left in them. Terra cotta pots I have left outside for the winter have all eventually cracked and become unusable. If you must store your terra cotta pots outside, stack them upside down and elevate them off the ground. Cover them with a tarp to keep them protected from rain and snow so they will not absorb water.
Containers made from materials such as wood, cast iron, metal, concrete, fiberglass, lead, plastic and dry cast limestone may be left outside in winter. When buying fiberglass or plastic containers, look for ones that are UV resistant, as sunlight can degrade the plastic over time and cause it to fade in color, become brittle and crack. In general, it is best to store ceramic containers inside even though the coating on these pots will keep moisture out for the most part. Small chips or cracks can allow water in and harm even coated ceramic pots. I do know of gardeners who have left their ceramic pots outside in winter over a long period of time with good results.