Back in the 1990s, the kids in my high school were convinced that banana peels contained a mysterious psychoactive substance that could apparently induce vivid hallucinations when smoked. I suppose it’s the tragic fate of the elder millennial that, 30 years later, the same people are now positive that the real excitement banana peels have to offer is in caring for their houseplants. With hundreds of social media posts touting the apparently transformative effect banana peels can have on plant growth, I set out to learn if there was any evidence for this claim.
Some proponents argue that the peel should just be laid to decompose on the top of your plant pots. (Sounds a delightful thing to have in your living room.) Others say it should be sealed in jars of water for a few days, before pouring the resultant “tea” on your plants. A third school of thought involves baking the peel in a low oven until it turns black, and grinding the charred skins into a powder to mix into soil.
The bottom line is that fertilisers boost growth by supplying the essential elements plants need, in particular nitrogen, phosphorus and potassium. So, how much do bananas peels contain? There have been a range of studies that have investigated this question, and although they often looked at blends of banana peels with other ingredients like manure and bone meal, they all returned similar results. The peels have much lower levels of the three major nutrients than . While they do contain a decent amount of potassium (essential for flower and fruit formation), their levels of nitrogen (essential for leaves) are minuscule.
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As most houseplants are grown for their leaves, not for their fruit, this means banana peels wouldn’t be a great choice, especially as they are weaker in all essential nutrients than standard commercial plant food.
However, they do have one big advantage: they are free, not to mention environmentally friendly. So, could the cost- benefit make it worth it? If you incinerated the peels into ash, then perhaps. (Everyone has the kit at home to do that, right?) But simply adding the skins to water for a few days will only extract a tiny fraction of these minerals. Similarly, even if you were to brave the idea of leaving them to rot in the pots around your apartment, the sterilised potting mix used for houseplants is unlikely to have the microbial life to unlock the minerals in the peel into a form your plants can use.
So, theoretically, yes, banana peels can be used to make fertiliser industrially, when combined with ingredients richer in the minerals they lack and processed in ways you can’t easily replicate at home. But the reality is they make as good a houseplant fertiliser as they do a smoking material.
James Wong is a botanist and science writer, with a particular interest in food crops, conservation and the environment. Trained at the Royal Botanic Gardens, Kew, in London, he shares his tiny flat with more than 500 houseplants. You can follow him on X and Instagram @botanygeek
For other projects visit newscientist.com/maker
