Bananas (Musa spp. and Ensete spp.) are spectacular plants for the summer garden, with their thick “trunk” and their huge paddle-shaped leaves, creating a guaranteed tropical effect. Moreover, in recent years, they’ve gone from being obscure plants you had to order by mail to something commonly sold in the average garden center. Of course, the nursery figures you’ll be growing them as annuals, placing them on your deck or planting them in your garden for the summer, then letting them freeze to death in the fall.
But then there is the so-called “hardy banana” (Musa basjoo) that tolerates several degrees of frost as long as the cold doesn’t last more than a few hours and that can thus survive outdoors in zone 8 and sometimes even 7 under a thick mulch. And yes, we all know someone who has managed to get it through a zone 5 or even zone 4 winter with a massive degree of protection, including heating cables, but for ordinary gardeners in temperate climates, bananas are not simply going to be hardy outdoors.
So does that mean you have to let yours die this fall?
Of course not! You only have to bring it indoors. And here are two ways of doing so:
Bananas as Houseplants
If you have enough space to do so, you can overwinter your banana indoors by treating it as a houseplant. Obviously, dwarf varieties make the best indoor plants, because who has room for a 16 foot (5 m) banana “tree” in their living room?
Just make sure you bring the plant indoors relatively early, certainly before there is any risk of frost. Bananas really don’t like cold at all, so ideally you’d bring them indoors in early September while night temperatures are still warm, but, failing that, you really should get them indoors before outdoors temperatures start to drop below 50˚F (10˚C) at night.
Note that it is very unlikely that your banana will ever bloom and bear fruit in a temperate climate unless you grow it all year in a heated greenhouse, but if you want to have the slightest chance of ever seeing it produce bananas (edible or not) one day, do keep it growing throughout the year. Putting the plant into dormancy following the technique explained Forcing Dormancy below will definitely end any chance of it flowering.
If your banana plant is already growing in a pot, just clean it up (see Bring Your Plants Indoors… Without the Bugs for more information.). If it’s growing in the ground, dig it and it pot it up into a large pot using your favorite houseplant potting soil.
You’ll need a brightly lit room, preferably facing south and with large windows. If you have the budget for it, you can add high intensity artificial lights to help it grow better. (Warning: they cost mucho dinero!) And if you do so, you might as well add a timer so you can extend the daylength to 14 hours, as that will stimulate better and faster growth. Still, even in a normal window with no added artificial, your plant should be able to pull through the winter in decent shape.
During the winter, water regularly and deeply as soon as the soil is dry to the touch. Also feed with an all-purpose fertilizer at half the recommended dose. Stop feeding at the end of November and resume in early March so as not to stimulate etiolated growth while the days are short and therefore light is weak. (If you’re giving your banana intense artificial light, keep on fertilizing right through the winter.)
Average home temperatures down to 60˚F (15˚C) at night are certainly acceptable for bananas, but in fact they really prefer tropical temperatures at all times: nights above 68˚F (20˚C) and daytime temperatures above 75˚F (24˚C). So if you don’t mind superheating your home…
Ideally you would also increase the air humidity, either using a humidifier or a humidity tray or simply by surrounding them with other plants to create a “jungle effect”.
While the plant is indoors, remove yellowing leaves as needed: normally an established banana will lose one leaf for each new one it produces.
Finally, watch out for spider mites: they just love banana plants, especially when the air is dry. Be prepared to control them by spraying with a solution of insecticidal soap or an insecticide containing pyrethrum when they appear.
In early summer, when outdoor temperatures begin to remain above 50˚F (10°C) at night, you can start to acclimate your banana to outdoor conditions so it will be ready for its summer stay in the garden.
If you don’t have the space or light to keep a banana plant growing in your home over the winter, you can force it into dormancy. You see, Mother Nature gave the banana a backup plan: a large underground corm (bulb) from which it can resprout if things go wrong.
You don’t need to be in as much of a hurry to bring a banana indoors if you intend to store it dormant. You can wait until nights drop to 40˚F (5˚C) or even until there is a touch of frost, because you’ll be cutting off the foliage anyway and the corm, being underground, won’t be exposed to the most extreme temperatures. Besides, a little cold in the fall will help the plant prepare physiologically for the dormancy to come.
When frost really does threaten, bring the plant indoors and cut the trunk (actually a pseudostem composed of tightly packed, overlapping leaf bases) to about 4 to 8 inches (10 to 20 cm) from the ground. All it takes is a good steak knife to cut through the watery stem.
Place the stump and roots in a cool (about 45 to 50˚F/7 to 10˚C) but frost-free spot, possibly a barely heated garage, a root cellar or a crawl space. No lighting or watering will be needed during the plant’s dormancy.
In March, it’s time to wake up your banana plant up again. Place it in a warm and well-lit room and start watering and fertilizing. Soon a new shoot will appear in the center of the old pseudostem (if indeed it hasn’t already started to sprout) and the plant will quickly come to life. Begin to acclimate it to outdoor conditions when night temperatures remain consistently above 50˚F (10˚C).
Note that there must be 10 other variations on how to store banana plants dormant indoors over the winter. I’ve only covered one here, the one I use myself, but if you’re interested, you’ll find plenty of other techniques on the Internet.
Good luck overwintering your banana plants: it really isn’t that hard to do!