Growing banana trees in northern zones is one of those I’m-cooler-than-you gardeners’ bragging right things. They are gorgeous plants, easy to grow, and the challenge of getting a windowsill banana tree to produce fruit is one that I just can’t resist. However, there are a few problems that can show up when you grow these subtropical fruit trees indoors. They want to be outside, not in, and although bananas are pretty well-behaved, every now and then they do throw a wee little bit of a tantrum.

If there’s one thing I hope you have figured out by now in your adventures growing banana trees, it’s that the leaves are fragile. For many of us, the most common problem we run into when growing banana trees indoors is the darn leaves – they seem to split with the least bit of provocation. Why do they do it? Can it be avoided?

Well. Sometimes.

MISTAKES GROWING WINDOWSILL BANANAS TREES: OVERWATERING

Watering your banana tree to keep the soil at the right moisture level is where you can expect to see some of your biggest issues show up – but the problems might not be easy to diagnose at first. The banana is a subtropical fruit tree, and it doesn’t behave like the cold-climate fruit trees that most of us northern-zone gardeners are used to growing in our orchards.

If, for example, I overwater a cold-tolerant deciduous tree to the point where its roots are constantly drenched, I can expect to see the tree start to wilt as it begins rotting out from the roots up. The banana, on the other hand, starts to signal overwatering in the texture of its leaves. As too much water is dumped on the roots, the tree just tries to suck it all up – damaging leaf integrity. Your first warning sign of overwatering is often an ugly split along these massive leaves, because they are just too fragile to handle that much extra water. It’s like one of those watermelons you might find in your garden after a wet summer, a nice juicy globe that you slice into and find the fruity interior is just falling apart; you can also compare it to a tomato on the vine that splits wide open after a rain.

“Perfect!” You may cry. “Overwatering! That explains why my banana looks so stressed!”

Well, maybe. Unfortunately, there’s other reasons why your banana tree may have split leaves. When you’re considering the diagnosis for split leaves, you can rule out a water problem by checking the soil – if it’s soggy and the split is recent, you’ve probably found your problem. The tree will recover if you let the soil slip back into a more reasonable moisture level; the split won’t heal, of course, but the tree will be just fine until it has time to grow a replacement.

MISTAKES GROWING WINDOWSILL BANANAS TREES: ABRASIVE AIRFLOW

In their natural growth environment, bananas are – obviously – stuck contending with outdoor winds. When these winds are more aggressive than normal, the natural response of the tree is to let the fragile leaves shred. I’m not exactly the world’s expert banana psychologist, but it makes perfect sense to me; subtropical winds CAN get pretty wild (hurricanes, anyone?) and if I was a tree, I’d rather let the current leaves tatter to pieces than let them get yanked right off. A shredded leaf is not super-efficient, but it’s still good for something while the replacement grows in!

Now, I’m hoping your windowsill banana tree won’t have to contend with any hurricanes. However, banana trees grown indoors still do face some airflow problems.

First and foremost, if you are buying a large-ish banana tree to grow in your house, how are you getting it home? In the back of a truck? I hate to break it to you, but depending on how fast you’re driving, that equates to some pretty darn high wind speeds… and yes, I do in fact have some personal experience in this area. Highways in my rural area are 55mph, and let me tell you, that transported tree looked ROUGH. Oops. (The tree did survive, though, in case you are wondering!). So be careful about your speed when transporting, and if possible, keep the tree IN your vehicle, rather than in an open truck bed.

Another “high winds” situation that a windowsill banana tree may face is when you set it in a windy outdoor location in the summer. Based on your area’s typical weather conditions, you should have a pretty good idea of how much protection you should plan on providing for your banana tree. 

Make sure you calculate in the effect of surrounding structures when you are trying to figure out wind impact on your patio. Buildings, hillsides, and other tall structures can act as funnels that amplify wind pressure and direct it in unexpected directions. Ideally, the side of your house will serve as a wind break for a potted banana tree set out on a patio for the summer.

However, in a less-than-ideal situation, the side of your house will conspire with other surrounding structures to create an obnoxious wind tunnel that sends a heavy breeze tearing at the leaves of your tree. This wind usually won’t be enough of a problem to knock the pot over, but it definitely increases your chances of shredded leaves.

Additionally, you should consider the location when you put a potted banana tree on the windowsill. This is particularly important when structures are arranged just right to direct air pressure through that open window. Wind picks up speed over open ground. In my area, “open ground” is most likely to be cornfields. Waterfront properties are also more likely to have higher winds due to the speed picked up over open water. 

Finally, your banana tree may face “wind” pressure from something as simple as your home’s air circulation system. Now, the majority of indoor fans are slow… like REALLLLLLLY slow. Ceiling fans, for instance, are slower than slowest – pretty sure they range like 2-3 mph, and if they ever hit an airflow of 5 mph I’d be downright shocked – and any impact on your banana tree is going to be absolutely nil. If you have a generic plug-in window fan, chances are it’s still at a pretty low speed; however, if you have a shop-quality fan that is constantly directed at your banana tree, even a relatively low-grade stress that never lets up can cause some splits now and then.

TROUBLESHOOTING WINDOWSILL BANANAS: MORE RESOURCES

I’ve been growing bananas for a while now, so I’ve had lots of time to make some (pretty stupid) mistakes. This article is just the first in a series of how-to (or rather, how-to NOT) articles I plan to put out on growing windowsill bananas. In reality, banana trees are simple to grow, even in northern zones and they are a fabulous addition to your windowsill garden… there’s just a few problems here and there to be aware of, and hopefully now you can at least track down the culprit behind the problem of split leaves.

As always, I would recommend looking up other expert resources – not just blogs! – for information on how to grow your windowsill trees. One of my favorite resources for growing bananas is the Texas Cooperative Extension’s excellent article on growing bananas; unfortunately for northern gardeners, the article is geared toward those in warmer climates (it IS a Texas article, after all) who can grow bananas in their backyard, rather than on their windowsill. However, the biology of the banana tree is the same whether you grow it indoors or out, so the information is still pretty useful. Just don’t forget to adapt the suggestions to better fit the needs of an indoor growing environment!

Not sure where to purchase a started potted fruit tree? Check out my favorite windowsill fruit tree nurseries!