In most areas transplanting plants in the winter time is not normally a recommended practice. The plants are dormant at this time of year, will not be able to fight off freezing temperatures that the roots might be exposed to, and digging in frozen soil is not always an easy task. However, if you have to move a plant in the winter and you don't live in a warm climate like Florida, there are a few things you can do to keep the plant alive until the next growing season.
Dig a new hole for the plants, making it as wide as you can. Dig as deep as you feel the root ball will be. A little deeper than needed is better than not deep enough—it will be a quicker and easier to fill the hole in with a little dirt to raise the plant up than it will to stop and dig a deeper hole. You don't want the plant out of the ground for too long.
Chop up the ground at the bottom of the hole with a shovel and mix in a small amount of compost to give the roots nutrients, and to aerate the ground for better drainage.
Mix compost in with the soil that you removed from the hole for added nutrients.
Dig a hole around the plant you are moving that is about the same size as the new hole.
Move the plant and quickly fill in the dirt on top of it. Tap down with your foot to press the dirt in place to the point where the plant will stand up on its own. With smaller plants, your hand will suffice.
Water the soil lightly so that it is damp, but not soaking wet.
Cover the area around the plant with mulch that is at least 2 or 3 inches deep. This will insulate the ground and protect the plant from freezing temperatures.