Indoor gardening is all about sharing: the sharing of plants and the sharing of information about them. Much of the information sharing takes place online—where gardeners can access a wealth of information and/or fall into a trench of deception. It’s kind of a crap shoot whether a google search comes up with dubious myths or accurate science. One of the internet plant myths that won’t die is using kitchen trash in your plants.
I’d say the most popular trash-for-plants myth is soaking banana peels in water and using that to water your plants. As a daughter of a former banana farmer, I am no stranger to the 101 things you can do with bananas. But never did we use banana as a fertilizer. First off, in order to be classified as a fertilizer, there has to be an NPK value, three macronutrients essential to plant health – nitrogen, phosphorous, and potassium. These are often represented by little numbers on fertilizer containers. Bananas have no NPK value and therefore cannot be classified as a fertilizer.
Bananas are known to be packed with nutrients, especially potassium, but did you know dozens of other fruit and vegetables contain MORE potassium than bananas? A medium sized baked potato has twice as much potassium as a banana. Avocados, papayas, pinto beans, and tomatoes (this list goes on and on) also have more, but you won’t find internet advice about adding these to your houseplant water. I suppose bananas are more fun.
Additionally, as bananas break down, they will eat up nitrogen in the soil that’s vital for plant growth. This is true for a lot of food waste. In the long run, it can inhibit plant growth. Not only that, banana water is a great way to attract fungus gnats into your house, which is one of the top houseplant problems people also google about (and receive false advice as a result—saving this for a future rant!).
Egg shells and coffee grounds are also commonly hyped up as great additives to houseplants and garden beds. These, too, should be avoided for similar reasons. They contain minimal nutrients and do little to benefit your plants.
Coffee grounds in particular cause more issues than benefits. Caffeine may be great for humans (debatable), but it’s bad for plants. The extra boost we get can do the exact opposite for plants, actually inhibiting growth in many species.
Perhaps the reason more people are trying to utilize material like this in plants is because of the noble call for sustainability. But matter like coffee grounds, eggshells, and banana peels quickly break down in compost piles. There are better ways to be more sustainable in our plant-keeping —and that’s another rant for the future.
The best of all reasons to compost food waste is to keep it out of landfills. Even if it is never used as.compost decayed food waste, once the water is gone, takes up virtually no space. We had a compost heap for over thirty years that never exceeded the bounds of the pen.
Definitely in compost, but not as top dressing or sticking things in plant pots!
Johanna, thanks for an informative post. It might be helpful if you made the difference clear between adding coffee, eggshells or banana skins DIRECTLY into the garden or pots versus composting them and putting the finished compost into pots or the garden. IMHO, there’s a big difference in potential harmful effects.
Yes – this is a serious specifically to houseplants and indoor gardening so definitely it is great in compost but not directly into pots or gardens.
Thank you so much. I’d been planting banana peels under new roses, and put coffee grounds in everywhere there was some soil free.
I used to put eggshells in the earth too, but our local raccoon digs them up and brings them to a small bird bath.
40 years of habits I can jettison. Thanks! Hope to read more from you!
Coffee grounds are great for acid loving OUT DOOR PLANTS. They change soil structure & acidity. Especially in the South! Azaleas,Gardenias,Camilla & Ferns. Dig it in to top soil. Your plants won’t turn yellow! THAT SAID,anything in a pot will respond differently than in ground no matter what you put in it. Always check labels 1st! I found out using a systemic on potted outside rose bushes was a NO NO! ONLY USE ON INGROUND PLANTS. In house plants usually turn yellow,because they are over watered. My favorite thing to do is finding ways to root different types of plants. It’s amazingly simple for many plants.
The coffee grounds being more acidic and helping plants is also somewhat of a myth. Unless it is SUPER acidic it is unlikely to actually acidify your soil: https://www.gardenmyths.com/coffee-grounds-acidifies-soil/
Hold on a minute! Because someone writes something in a blog doesn’t necessarily make what they write factual. The process of decay returns nutrients including nitrogen to the soil. It’s part of the nitrogen cycle…high school biology! Bury your banana peels if you like. I put them and other food wastes in my compost bin!
This is a houseplant post, for the most part, which is very different.
Composting 101: Don’t put fresh food waste into the soil under or around growing plants. The process of decaying underground will pull nitrogen away from the plants’ roots.
Interesting that a blog about misinformation on the internet gives misleading information. Saying it’s not fertilizer unless it has an NPK is misleading. That is looking at gardening from the chemical companies and agribusiness point of view. Maybe it’s a legal term defining what can be put on a label? There are countless nutrients in the soil that are crucial to the health and well being of plants, many of which come from decayed organic matter. Yes, NPK are essential nutrients, but they are not the only nutrients that feed plants. Plants have survived and thrived on earth since almost the beginning without fertilizer labels stating the NPK ratio. In fact, saying a fertilizer is a fertilizer only if it has NPK is like saying wonder bread is healthy because it has added nutrients.
This is not to say your advice not to water with banana peel water or throw coffee grounds on houseplants isn’t good advice – it is. That’s something I never would have dreamed of doing. And I’m very thankful that there are other foods besides bananas that I can get my potassium from.
I don’t dispute that coffee grounds have little value as a fertilizer per se, but out in the garden their main value is to draw earthworms, that ultimately fertilize the soil with their castings. Worms love coffee grounds, as any fisherman can attest.
I love it! Best advice I got from the internet regarding peels is to pre dig holes for food waste and cover it. Lets my compost pile be yard waste only. I had to learn quick to stop putting any fruit in my worm bin.
When I think of pervasive houseplant advice that is probably egregious but maybe a genius heuristic since The Internet says so, I think of watering with ice cubes.
This entire post was extremely informative! Thanks to everyone who commented.
leave the peels and fruit gone to far off to eat out my the hummingbird feeders, fruit flies are great protein for growing hummingbirds and they add so much to the garden, the hummingbirds,not the rotten bananas.