If you believe the hype the internet tells you, banana tea sounds like the holy grail for houseplants. Apparently super-nutritious and rich in phosphorus, potassium and magnesium (plus it makes use of banana peels which would otherwise go to waste). Or so they say. Are banana skins worth the hype for our houseplants, or do they do more harm than good? Let's find out...
How banana peels are used for plants
Outdoors, gardeners might put fresh banana peels in the holes dug for plants, often recommended for roses and other flowering plants. Sometimes they'll sprinkle dried, crushed banana peels on the soil. Or keep a bucket of banana skins 'brewing' in water, then water with the resulting 'banana tea'.
Indoors, houseplant hobbyists are more likely to cut up then soak the banana skins in water for a few days to make banana peel tea to later water their plants with.
Are banana peels good for plants?
Firstly, banana skins are organic matter, and ALL organic matter can potentially be good for our plants, provided the plants have a hand breaking down that matter into the nutrients they need.
Good guys like beneficial fungi and bacteria in the soil break down organic matter to release the nutrients for our plants to uptake.
Which shouldn't be a problem in healthy 'alive' soil outdoors, but indoor plants don't have the same population of good guys to do that job.
That's also why so many houseplant fertilisers are not organic. Like Growth Technology (GT), and Superthrive. They offer indoor plants the nutrients in an immediately available form, no fungi or bacteria required to act as the middle guys to break it down first.
That's the first red flag against bananas for our green buddies growing indoors. I wouldn't say harmful, just pointless. Except...
Pests and banana peels
Another red flag for us houseplant hobbyists... Guess who else loves rotting organic matter? Yep, fungus gnats! And for that matter, fruit flies too. Using banana peels for your plants can attract pests. That's a big no thank you from me and means it shifts from pointless to harmful in my books.
PS: Already have annoying plant flies all up in your face (and chomping on your plant's roots)? Here's how to get rid of fungus gnats once and for all >
What's the nutrient value of banana peels?
Seems like this should be such a simple question to answer given how often I see the advice to give plants banana peel tea. But surprisingly, no.
I have to give credit to the excellent plant myth buster Robert Pavlis from Garden Myths for doing the dirty work to find this one out (thank you!).
The NPK value for dried banana skins (that's after the water's removed), averages 0.6-0.4-11.5
(NPK = Nitrogen-Phosphorus-Potassium)
The NPK value for fresh banana skins before being added to water, averages 0.1-0.1-2.3.
So as you can see, pretty low. Also no higher in potassium than most fruits and veges. In fact other food scraps like potatoes potentially offer more potassium and magnesium. Unlike a lot of other plant matter, banana skins are a lot lower in nitrogen too.
That means if banana peels are your plant's only source of nutrients, your plant would likely be in trouble before long, with a nutrient deficiency the more likely outcome.
What should you do with banana peels?
By all means save those banana skins, but I'd be putting them in your compost, not your plants. Even for outdoor plants there's little to gain. I'd let your compost do its thing and use that for your outdoor plants instead.
And for your indoor plants? Without the ability to break it down combined with the added risk of attracting bad bugs, using banana skin tea for houseplants is a big no thank you for me.