Most people have no idea that they can grow a banana tree in temperate zones. Bananas are very much a tropical plant that prefer warmth and humidity, so the only way they grow in areas that freeze during the winter is by transplanting. Since bananas need almost 18 months of growth before they can produce a bunch of bananas, you will have to follow a few steps to move them indoors and keep them warm during the winter months.
Things You'll Need
Large plant pot and tray
Decide to move your banana plant indoors when the outside temperatures stay below 50 degrees consistently every evening. If you have a sudden cold snap, wrap the plant in a blanket or burlap covering to protect it from the frost. If you do forget to cover it and the plant seems to have died, there is a chance that it is still alive underground. Dig up the rhizome as described below and bring indoors. After a few days, if there is still life, it will sprout new growth.
Trim the plant. Bananas trees can grow upwards of 6 feet and will need to be cut back before transplanting. Remove the large outer leaves from the stem with a sharp knife. Cut back the main stem to about 3 feet high.
Remove any sizable shoots that have sprouted off the main rhizome by slicing them cleanly with the knife. These can be repotted and brought indoors to stay warm until spring arrives. If they are too small, they probably will not make the winter, but it does not hurt to try.
Carefully pull the dirt back from the banana tree exposing the underground rhizome and roots. Dig around the entire plant, slanting your shovel in toward the center until you have a nice ball of dirt. Be sure not to slice the main rhizome. Lift the root ball from the ground and place it in a planting pot. Fill in any holes with potting soil.
Move the newly planted banana tree inside to a warm and sunny window. Water and fertilize regularly, but do not let the soil get soggy. The plant should have very good drainage. Rotate the banana tree every week so that it gets light on every side. It should continue to grow, although much slower than outside, unless you have superior lighting and humid warmth in your house.
Once the weather has warmed and all danger of frost has passed, the banana tree can be moved back outside to continue its growth. Just remember to keep the soil loose and well drained and fertilize regularly as it is quite a heavy feeder. Once the fruiting stem emerges, a cluster of flowers should form and then bananas will follow. After fruiting, the plant will die back and will need to be removed. New plants will continue to grow off the side rhizomes that form underground in the same manner as the main plant.