Type Is Important For Winter Success
If you're over-wintering potted plants outdoors, you should consider the
container's frost tolerance along with its hardiness rating. Some clay pots are
frost-resistant, having been fired to extremely high temperatures, and are
labeled as such. Concrete, plastic, and the newer resin pots will withstand the
rigors of winter in most areas of the country, and are good, safe choices. Just
check the label on the pot you select, or ask for advice at your local garden
Trees And Shrubs In Winter
If a tree and its container are movable, consider an unheated garage as a safe
winter haven. Once a tree or shrub has gone dormant, light isn't a factor, but
moisture is. Plants housed in garages will need supplemental watering over the
course of the winter, especially when temperatures rise.
Outside, extra protection will need to be provided. If at all possible, move the
container to an area protected from drying winter winds. Up against your house
on the north or east side are excellent spots. The larger the pot, the more soil
that surrounds the roots, increasing insulation.
What About Deciduous Potted Trees?
Deciduous trees and shrubs (those that lose their leaves in winter) suffer less
in winter than evergreens do because of moisture loss through their leaves and
needles. Erecting a windbreak, or loosely wrapping the tree with burlap, can
provide protection from desiccating winds. Leave an opening at the top and
bottom of the plant for air circulation, and never EVER use plastic sheeting.
Protect The Roots Of Potted Plants During Winter
Extra insulation for a potted tree's root system is necessary to keep it from
freezing in the winter. Roots are the most cold-sensitive part of a plant. The
"pot within a pot" method can be used to provide extra protection.
Place your container inside a pot that is at least three to four times larger,
and fill the space between with bubble wrap, leaves, layers of burlap, or mulch.
Normal garden mulches can be used over the top of the root-ball as long as water
can penetrate the mulch. The pot's contact with the ground also helps to
somewhat moderate its temperature.
An alternative to the "pot within a pot" method is to construct a
loose cylinder of chicken wire around the pot and fill it with chopped leaves,
bubble wrap, or layers of burlap. Remember, if the winter is dry you may need to
water your container plants. Do so on a warm, non-freezing day.