Bananas are tropical plants and require a combination of warmth, bright light, and moisture/ humidity. These conditions are generally easy to provide indoors and should be provided year round.
Indoor temperatures in a heated home will generally be somewhat drier than in nature. See "Humidity" for suggestions on increasing indoor Humidity for Banana Plants.
Most local nurseries don't carry banana plants, ordering them online is best . Some banana tree varieties will produce edible fruit, others will not. Musa basjoo does not produce edible bananas for instance, while Cavendish does. Therefore, be sure of the type of indoor banana tree you want to be certain that it will accommodate your needs.
Reputable sources for Banana Trees
Use a light soil mix that drains well, it should have a high percentage of vermiculite, perlite and peat in it. If you are going to use potting soil add about 20% of vermiculite and or perlite and another 20% of peat. If you are hell bent on using soil from your yard - stop reading now - your banana plant is going to die.
An acidic mix with a soil pH between 5.5 and 6.5 is best.
Any container you use should have drainage, at least one drainage hole at the base , preferably more. Should your plant outgrow its container - transplanting to a larger container later is not much of a problem. Bananas will cease growing when they become pot bound, so an adequately large container is essential.
Plant the rhizome upright and cover the roots well. Be sure to leave a tad of the rhizome aka corm exposed, about one fifth should be above the soil level, exposed to light till the plant develops a few new leaves. Once the plant has matured somewhat you can cover the rhizome completely which will promote healthy root development.
Fertilize monthly, especially when the plant starts producing fruit.Banana plants require basically the same nutrients as all plants - nitrogen, phosphorous and potassium. Potassium being vital for bananas. Macro-nutrients they crave are calcium, magnesium and sulfur. A fertilizer high in "K" or potassium is best for fruit production.
A 6-2-12 fertilizer with magnesium is best when the plant is starting its first bearing year. When the plant matures use 8-10-8. Pour it around the base of your plant evenly. Immature Dwarf Banana Trees should receive a fertilizer mix of about 1/3 of what the package suggests for a mature plant.
Over feeding will cause the leaves to be deformed and the plant will hence produce poorly. Under feeding is not as damaging so long as the plant is receiving some nutrients - with bananas , in particular dwarf varieties less fertilizer is at times better.
Bananas, like all tropical plants, require abundant light. Grow lights are great but a southern exposure will suffice. 10 to 12 hours of light is optimal for most varieties.
Rotate your plant periodically to make certain that all sides receive light, you'll end up with a very lopsided plant otherwise.
Naturally being tropical - warmth is also a key element to successfully growing bananas. The optimal night temperature should be 65° F to 70° F. Daytime temperatures in the 80s.
Bananas need lots of water to support their abundant foliage, don't drown them,, just be sure they are persistently watered. Keep the soil evenly moist, a layer of bark mulch or coco coir mulch will help the soil retain moisture.
Allow the soil to dry between watering, not dry-out completely - just dry. When the soil is dry to about a 1/2 inch depth it is sufficiently dry.
I generally water every other day, not a saturating drench - just a healthy watering.
Humidity is vital, artificial - indoor heat leeches humidity out of the air. Any building that has heat or air conditioning will usually have no more than 15% humidity at most. Bananas need about 50 percent, or higher humidity in the plants immediate vicinity.
Significantly increasing humidity indoors is good for the plants , but it's not good for you or your home unless of course you like mold, mildew, bacteria, mites and so forth.
There are a number of ways you can increase humidity for the plants without seriously damaging your personal environment.
1. Humidifiers You can add moisture with a humidifier.
2. Cluster your plants in tight groups. All Plants naturally exhale moisture through their leaves in a process known as transpiration, Banana trees are no exception. By grouping indoor plants together, you add to a more suitable environment in the immediate growing area.
3. Misting the trees foliage with a simple spray bottle is good way to help banana trees cope with the indoor environment.
4. Humidity Trays
You can add moisture with humidity trays which will enhance the development of indoor fruit trees, a pebble filled tray with water added to the top of the pebbles. As the water gradually evaporates, it raises the humidity in its immediate vicinity enough to improve conditions for the tree.