Climate plays a role in container
gardening because it depends on what you're growing and when your growing it. You don't need to worry about winter if you are into single-season containers. However its still important to know when the weather has warmed up enough in spring so it's safe to set out tender plants that can't tolerate frost.
If however, your containers
are filled with permanent plants - perennials, trees, and shrubs - then you need to tune in more carefully to the regions climate. In most cases, winter temperatures are the deciding factor in what will survive in your climate.
A great tip to remember is that growing plants in containers
allows you to grow plants that otherwise may not survive in your climate if you are willing to take extra steps to protect them in extreme temps - like moving them to protected spots.
As you already know, container
plants are more vulnerable to extreme temps (especially cold) than the same plant growing in the ground. Soil temps rarely drop below the 20's but because of the soils residual heat. The soil in containers can freeze solid when exposed to cold temps. Temperatures that alternate between freezing and thawing post another challenge. On a sunny winter day they soil may thaw and then at night refreeze when the temperatures drop. Once soil freezes again it expands and push plants up out of the soil. This is the time that a ceramic
or clay pay will crack.
Knowing the frost dates for your region is kind of like peering into a crystal ball. If you move your containers to a sheltered place for the winter, the plants may being sprouting earlier in spring than they would have had they wintered outdoors. Then, if you bring the plants outdoors before the last spring frost date the chances are good that the new growth will be nipped by frost. To be safe, if overwintering plants have begun to sprout in their sheltered spot, wait until after the last frost date to bring them outdoors.
To be totally successful, you really do need to keep an eye on the weather, especially in fall
when cold snaps can threaten warm season plants. We advise you move small containers
into a garage or enclosed porch, where temps stay a few degrees warmer than outdoors. Move them back when the threat has passed.
Cover large planters
with old sheets, cardboard boxes, or anything that holds heat. Use stakes to prop up the cover to avoid breaking stems. Extend covering all the way to the ground, and secure it around the base of the container to help hold in the heat. Remove covers the next morning once temps warm up to the 50's.