Some gardeners do much of their gardening and landscaping in pots and containers. People often ask me if containerized plants will survive the winter. The answer is, it depends.
Plant survival depends on how low the temperature drops in winter. We have many sunny days with above-freezing temperatures, yet temperatures drop below freezing most nights. If a plant freezes and thaws repeatedly in its container, it is stressed, weakened and less likely to survive. When a plant is in the ground, the soil buffers the freeze/thaw cycle. Placing pots on the north side of a building in the shade can reduce the frequency of thawing.
During much of the winter, we have very little rain or snow, often not enough moisture to soak a plant thoroughly. Because container plants dry out more readily than plants in the ground, they need to stay moist even in the winter, particularly on sunny days.
Containers vary. Clay pots wick the moisture outward, drying the soil within. Clay and ceramic pots can crack and break if the soil in them absorbs water, freezes and expands. Black plastic pots absorb heat during the day, which can dry out soil. However, they conduct cold at night, chilling or freezing roots. Wooden containers can sometimes moderate heat and cold fluctuations better than other types of containers.
Finally, some plants are hardier than others. Perennial flowers may sometimes survive in a pot, but roses are often killed in containers over winter. Trees and shrubs rarely do well in pots over winter, unless the containers are huge with large soil volume.
What can a gardener do to increase the chances of survival of containerized plants over winter? Heel them in; dig a trench and bury the containers in the ground or mound soil and mulch around a container above ground. On the other hand, you could remove the plants from their pots, put them in the ground, and water and mulch them. They will be ready for transplanting back to containers in the spring. I have had success creating wire mesh cylinders around my containers from the ground to the top of the plant and packing the cylinder with straw, mulch and leaves as insulation. If we are lucky enough to get snow, mound snow all around and over your containers and pack it tight. Unfortunately, this only works if it remains cold and the snow sticks around for a while.
With a bit of insulation and attention through the winter, potted plants can survive.
JoAnne Skelly is the Carson City/Storey County Extension educator for the University of Nevada Cooperative Extension.