Bananas are tropical plants requiring high temperatures and humid conditions for their fruit (bananas) to grow and ripen. It is possible for virtually any home gardener to start a banana plant growing at home, with little more than a plastic bag. It helps if the home gardener has access to an existing banana plant, but if not a banana start, called a "corm" can be ordered online.
Obtain a banana tree corm, also known as a bullhead. This is a portion of the tree's root that will sprout a new tree. Corms look like large bulbs growing on the roots of the banana tree. Use a sharp knife to cut off a corm from the root of an existing tree or order a corm online.
Cut off the bottom half of the corm horizontally, using a sharp knife. There should be one or more "eyes" on the top side of the corm, similar to those on a potato.
Place the corm in a pot of hot water (125 degrees F; use a thermometer to check the temperature) for 20 minutes.
Remove the corm from the water and place it in a plastic bag. Seal the bag and place the bag in a warm location, preferably 75 to 85 degrees F.
Check the bag every couple of days. Watch for roots to form on the corm. When the roots are 1 inch long remove the corm from the plastic bag and plant it (roots down) in a growing pot filled with potting soil. Plant it approximately 1/2 inch deep. Keep the soil damp at all times and keep the pot in a sunny room. Bananas sprout fastest when the temperature is kept between 75 and 85 degrees F.