Container Gardening in the Winter
I know a lot of you container garden everything from fresh herbs to small trees. The question becomes what do you do with those containers in the winter. There are actually a few ways to protect your perennial plants without having to bring them inside. This is really helpful if you don't have much room to spare inside for a lot of plants or larger pots. If your pots are clay or terra cotta it's likely they will crack if left outside. Stoneware of any kind should not be left outside over the winter whether they are planted or empty. The freeze and thaw cycle will break them. Plastic pots actually do very well outside. The only thing to be concerned about plastic pots is they don't handle UV very well and will often degrade after a couple of years making them susceptible to cracking or breaking when you try to move the plant.
Smaller plants can be transplanted to the garden to overwinter...if you have a garden...then transplanted back to a container in the spring.
For mid-sized pots you can bury them in the ground. Bury them up to their rims. Make sure the soil in the pot is moist then mulch the top of the pot with leaves or straw. A thicker layer of mulch will help prevent the roots from freezing. You can of course do this with large pots they just take a bigger hole and are generally much heavier to move. If you have a garden that makes this method a lot easier since the soil is a lot easier to dig in.
If you can't or don't want to dig a hole then move the containers to an inside corner of the building. The east or north side of the building works best since the sun won't vary the temperature there. Then mulch the pots heavily with straw or leaves. Make sure the pots are completely covered. At least one foot of mulch. Two or three feet would be better. The air space in the leaves or straw will add insulation and the building will provide the heat. If you have really cold temperatures or you expect a period of below zero then you can wrap a tarp or other material around the mulch to help insulate a bit more. If you have to remove larger plants from a stoneware pot then lay them flat with their roots covered by as much dirt as you can save from the pot. Then cover the whole plant with mulch. Again, at least 1 foot thick.
Finally, you can move the plants into an unheated garage or outbuilding that holds temperatures above freezing. Just make certain to water the plants periodically because they will dry out in a garage. You don't need to add a lot of water. You just want to keep the soil moistened. If the building doesn't have heat then use the same method as the inner corner above.
Remember that snow is your friend. It adds additional insulation to the plants and helps keep them from freezing.
