Banana Water for Plants: Does It Actually Work?
GardeningNorm is reader-supported. As an Amazon Associate, we earn from qualifying purchases — at no extra cost to you.
Banana water is mostly harmless and mostly not worth the trouble: it is not a fertilizer. A banana peel does contain potassium, but the University of Maryland Extension says it knows of no scientific studies on using banana peels as fertilizer, and the experts who have commented on soaking say very little potassium ends up in the water. If you want the peel’s nutrients to reach your plants, compost it first; if a plant is actually hungry, feed it with a real fertilizer.
| What you do with the peel | What reaches the plant | Main risk | Verdict |
|---|---|---|---|
| Soak it in water (“banana water”) | A small, unmeasured amount of potassium; experts call it negligible | Fungus gnats, mold and a sour smell if it sits in a pot | Optional at best. Outdoor soil only. |
| Spray the soak on leaves | Even less; leaves are not a shortcut here | Microbes and residues on the foliage | Skip. |
| Bury raw peels near roots | Nothing until microbes break the peel down, which is slow | Rot pocket, animals digging | Skip; compost instead. |
| Dry and grind to powder | More surface area, but still needs microbes in the soil | Gnats in potting mix if overdone | Light use outdoors. |
| Compost or worm bin | Peel nutrients in a stable, finished form, plus organic matter | Almost none if the pile is managed | Best use. |
| Balanced fertilizer | Measured N-P-K on the label | Overfeeding | What a hungry plant needs. |
What is actually in a banana peel
The only detailed composition table I could verify comes from FAO’s Feedipedia feed database, and it describes immature (green) peels, so ripe peels will differ somewhat.
| Measure (immature peel) | Value | What it means |
|---|---|---|
| Dry matter | 13.1% as fed | About 87% of a fresh peel is water. |
| Potassium (K) | 36 g per kg of dry matter | The headline nutrient. Works out to roughly 0.5% of a fresh peel (my arithmetic). |
| Phosphorus (P) | 1.0 g per kg of dry matter | Tiny. |
| Calcium (Ca) | 3.5 g per kg of dry matter | Small. |
| Crude protein | 6.7% of dry matter | Dividing by the standard 6.25 factor gives roughly 0.14% nitrogen in a fresh peel (my arithmetic). |
Put that next to a fertilizer label. The three numbers on a bag are percentages by weight, so a 10-10-10 is 10% nitrogen. A whole fresh peel, before any of it dissolves in water, carries roughly 70 times less nitrogen than that. Potassium is where a peel looks respectable, and that is exactly why the myth exists. Estimates are not consistent, though: another garden-science site gives a dry-weight analysis of about 0.6-0.4-11.5 (N-P₂O₅-K₂O) without naming its underlying sources, and its potassium figure is a few times higher than FAO’s. Treat any single potassium number as soft.
Notice what none of these numbers tell you: how much of the peel’s potassium ends up in the water. I could not find a published measurement. Real Simple quotes garden consultant Jessica Damiano saying a soak might extract a negligible amount of potassium, and Epic Gardening says very little leaches out even after long steeping. Both are expert judgment, not lab data, but they point the same way.
Three questions to ask before you use banana water
- Is this plant short of potassium at all? Potassium shortage typically shows as scorched or browned leaf edges, starting on older leaves, but many problems look alike, and overwatering, low light and wrong pH are more common culprits. University of Maryland Extension’s advice for this exact question is to test your soil first. If the soil already has enough potassium, more won’t help.
- Does the nutrient actually make it into the water? I found no measurement showing it does in useful amounts (see above). A brown liquid proves nothing about nutrient content.
- Can the plant use it in that form? Plants take nutrients up from the soil solution; a peel has to be broken down by microbes before most of what’s in it becomes available. That happens well in a compost pile or worm bin, and poorly in a jar or a pot.
If the answer to the first question is “I don’t know,” the next step is a soil test, not a banana. If the answer to the second or third is “probably not,” you have your reason to put the peel in the compost instead.
When not to use banana water
| Situation | Why to avoid it | Do this instead |
|---|---|---|
| Houseplants in pots | Wet potting mix with decaying organic matter is where fungus gnat larvae feed and females lay eggs (Virginia Tech Extension). Leftover banana bits add to the problem. | A diluted houseplant fertilizer, and let the top of the soil dry between waterings. |
| Orchids and cacti | They prefer precise watering and little organic debris on the surface (Gardenia.net). | A fertilizer labeled for them, at a low rate. See our orchid care tips. |
| Leaves of vegetables and herbs | Peel soaks can carry microbes and surface residues; Gardenia advises never putting them on edible leaves. | Water the soil, not the plant. |
| Conventionally grown bananas, unwashed | Pesticide residue on the peel can end up in the soak. The RHS says to wash bananas thoroughly first. | Wash the fruit, or compost the peel instead. |
| A plant that’s already sick | You can’t tell whether it helped or didn’t, and a new wet, organic input can add problems of its own. | Find the cause first. For example, yellow tomato leaves aren’t always about nutrients. |
If you still want to try it: the low-risk way
I don’t think banana water earns a place in a feeding schedule, but if you’re curious, here is a version that keeps the downsides small. The timing is my own judgment: I found no tested guidance on how long a soak stays safe.
- Wash the banana before you eat it, or use organic fruit, to cut down on surface residue (RHS).
- Chop one peel into small pieces and cover it with a jar of plain water.
- Keep it short. Overnight to about a day is plenty; the RHS describes a few days, but longer soaks mostly add smell and microbes, not potassium.
- Strain it well and throw the pieces in the compost. Leftover bits are what cause the odor and the gnats.
- Pour it on outdoor soil, not on leaves, and use it the same day. Don’t store it: treat it as something that spoils. If it smells sour or looks fuzzy, discard it.
- Don’t count on it. Keep feeding the plant the way you already do.
That’s the whole recipe. There’s no dose to calculate because there’s no tested dose, and anything that claims a precise schedule (“two cups every other week”) is inventing one.
What to do with the peels instead
Nearly every credible source lands on the same advice: send the peel through a biological system first.
- Compost it. Chop the peel and mix it with dry material such as leaves or shredded paper so the pile doesn’t turn slimy. Finished compost gives stable organic matter and a mix of nutrients, and it’s the route both the RHS and Gardenia recommend. Our guide to why compost seems to vanish explains what’s happening inside the pile. If you don’t have space for a pile, a kitchen countertop compost bin keeps scraps tidy until you can empty them.
- Feed it to worms. Small pieces buried under bedding are the usual advice for worm bins. The resulting castings are a far better plant input than a peel soak; see vermicompost and worm tea.
- Dry and grind it (optional). Real Simple and Thrive both suggest peel powder as a more concentrated alternative to the soak. It still depends on soil microbes, so use a light sprinkle outdoors, not in a houseplant pot.
Curious about other kitchen-water tricks? We’ve also looked at rice water for plants.
When the plant really is short of potassium
Then the fix is boring and reliable. Get a soil test through your state’s cooperative extension office; it will report potassium and give fertilizer recommendations. A home soil test kit is a quick check in the meantime, but a lab report is more reliable. For potted plants, a liquid houseplant fertilizer used at the label rate gives a measured N-P-K you can actually plan around. Our guide to plant food vs fertilizer shows how to read those three numbers and avoid fertilizer burn.
FAQ
How long does banana water last? I couldn’t find a tested shelf life, so treat it as perishable. A sugary, organic soak left in a jar ferments and goes moldy; make it fresh, use it the same day and discard anything that smells sour.
Is banana water good for orchids or houseplants? Not a good idea. Small pots stay damp, and decaying organic matter on or in the mix is what fungus gnats like. Orchids and cacti do best with precise watering and a fertilizer made for them.
Does the banana peel help tomatoes and roses? Both have a folk reputation, but I found no study showing a benefit. The reliable move for either is compost or a fertilizer chosen from a soil test. One use the RHS does describe for peels has nothing to do with feeding: put green tomatoes in a sealed brown paper bag with banana skins to help them ripen, because ripening fruit gives off ethylene.
Can banana water hurt my plants? It’s unlikely to poison them, because it’s so dilute. The real harm comes from the side effects: gnats, mold, odor and wet soil. I found no dose testing, which is another reason to skip schedules and quantities.
Do banana peels keep pests away? Gardenia.net says there is no solid evidence that peels repel common garden pests, and in a pot they can do the opposite by giving gnats something to breed in. Healthy plants in healthy soil are the better defense.
Sources: Gardenia.net — Banana Peels for Plants: Miracle Feed or Myth? · Royal Horticultural Society — How to use old banana skins in the garden · Real Simple — What Is Banana Water and Is It Good for Plants? · Epic Gardening — Should you use banana peel water for plants? · University of Maryland Extension (Ask Extension) — Banana Peel Tea · FAO Feedipedia — Banana peels, immature, fresh · GardenMyths — The Magical Power of Banana Peels in the Garden · Virginia Tech Extension — Fungus Gnats
