Over wintering is the process of inducing a hibernating state to your plant or tree.
This is especially important when caring for your fruit trees and plants over the colder months.
There are two main kinds of methods.
Over wintering outside:
If you have a very large plant or tree it may not be an option to dig it up and protect it indoors. So, to make sure it survives that cold winter you need care for it as best as you can. Depending on the size of the tree/plant you may have to trim it down. Try to cut the branches back a little if possible for size purposes.
If you have a small tree you can cover it with some plastic, tarps, blankets or even a bucket. In the end you want it to be fully covered and wrapped properly. Not too tight, and not too loose either. Make sure that you do this right after your first frost. If it is too warm and you cover it up it will most likely get too warm, produce some condensation and possibly will cause some rot.
Depending on your tree or plant some may withstand colder weather on their own so you can wait later in the season to cover them up. Please reference your plants climate conditions. There are some plants that will go into hibernation on their own. Another good thing you can do is to add mulch or hay to the base of the plant, tree. This will help keep the trunk/stalk warmer and the soil underneath it as well.
Don't allow the roots to freeze. If you are growing bananas to be outside year round try to plant the roots a good foot underneath the soil to keep them from freezing in the winter. The banana plant is one of the few plants that you could cut down to about 4 ft, cover and mulch, and would grow back really well in the spring.
Over wintering indoors:
This is a great option if your plant or tree is smaller. You can dig it up roots and all and place it in your garage, basement or underneath your house. The main thing to remember is to not give it any light and to cut back on your watering to an almost bi-weekly time frame. Also make sure not to feed your plant when you are overwintering it. The plant/tree will hibernate, most likely drop all its leafs and be fine. Any growth that does happen during this period will be in the roots.
The ideal soil temperature and climate for over wintering is around 30-40 degrees. But, of course that depends on the hardiness of the plant or tree.
Now there is a big debate whether to all your plants to grow indoors all winter and not over-winter them. This is an option you have, but most plants/trees enjoy some rest time and will produce much better the following season by having a little time off. But, if your plant is very small over wintering might not be an option and I would suggest letting it grow further and get fully established. The smaller the plant the more delicate it will be to the cold and to over wintering.
So as a conclusion over wintering is great to do for your plants at it encourages rest, lets them survive in colder climates by protecting them and helps them to get more established. Make sure not to cover them too early in the season if you are keeping them outside. Also, remember to unwrap them when it starts to get warmer or they will over heat.
If you protect your plants every winter you'll be rewarded with healthy plants/trees every year.