Banana peels are often called a free potassium fertilizer, and there’s some truth to that. Peels are rich in potassium and contain little nitrogen, and a few studies have tested them in pots and compost. This guide covers what peels actually contain, whether banana peel water for plants is worth making, how to make banana peel fertilizer by drying or composting, which plants it suits and what to watch for. It draws on published reviews and studies plus gardening author Robert Pavlis’s analysis; practical steps that no study covers are marked as such.
| Method | What the evidence says | Verdict |
|---|---|---|
| Short soak in water (banana peel water) | Adds some potassium, not much else (Pavlis); short soaks haven’t been tested in the studies reviewed | Weak; use fresh if at all |
| Dried peel powder mixed into soil | Raised soil K to 88 ppm in a pot trial, but soil pH was 8.98 (Wazir et al.) | Works in small amounts; watch pH |
| Decomposed in soil | Gave taller pea plants than peels decomposed in water (El Barnossi et al.) | Good |
| Composted with other scraps | Peel and watermelon-rind compost reached 5.87% K but needed more N and P (Msuya et al., 2025) | Good, as part of mixed compost |
Sources: Pavlis, Garden Myths; Khanyile et al. (2024), Agriculture (reviewing Wazir et al. and El Barnossi et al.); Msuya et al. (2025), Tanzania Journal of Engineering and Technology.
What Banana Peels Contain
Gardening author Robert Pavlis at Garden Myths gives an NPK of 0.6-0.4-11.5 for dried banana skins. Fresh peels are around 80% water, so he puts them at about one fifth of that: 0.1-0.1-2.3. He rejects the 0-25-42 figure that circulates online: a peel that is mostly water can’t be 42% potassium.
A 2022 review, “Banana Peels: A Waste Treasure for Human Being” (Hikal et al.), reports that dried peels contain 6 to 9% protein and 20 to 30% fiber, that lignin rises from 7 to 15% of dry matter as the fruit ripens, and cites earlier work naming potassium as the most important mineral in the peel. The takeaway: peels are a potassium source with very little nitrogen. Nitrogen drives leafy growth; potassium supports water regulation and overall plant health. Used alone, peels won’t feed a plant fully.
Banana Peel Water for Plants: Worth It?
The popular method is to soak peels in water for a day or two and pour the liquid on plants. Pavlis says the tea might add some potassium but not much else. Potassium dissolves readily, but a fresh peel holds only about 2% of it to begin with, so a short soak gives a weak solution.
Longer decomposition has been studied. The review by Khanyile et al. (2024) describes work by El Barnossi and colleagues in which peels were left to decompose in water or in soil for 2, 4 and 6 months and tested on peas. Peels decomposed in soil produced taller plants than those decomposed in water, and the authors found two months in soil the best period for growth. A 24-hour soak was not part of that work.
How to Make Banana Peel Fertilizer: Dry and Grind
Drying removes most of the water and concentrates the potassium. In the pot trial by Wazir et al., described in the Khanyile review, peels were dried in the sun, cut into pieces of about 1 cm, and 20 g of the dried peel powder was mixed into 4 kg of pot soil. The soil was left for 60 days before sowing to let the peel break down. At sowing, the soil had 88 ppm potassium and was alkaline, at pH 8.98. Another study in the review dried peels in sunlight for 5 to 7 days before crushing them into a powder.
A practical home version:
- Dry the peels in the sun or a low oven until they snap. Scrape off leftover fruit first.
- Grind them into a coarse powder in a blender or coffee grinder.
- Store in a sealed jar somewhere dry.
- Mix a small amount into the soil, ideally a few weeks before the plant needs it, since the trial let it break down for 60 days. The trial rate was 20 g per 4 kg of soil; for a typical 6-inch pot, a teaspoon or two is a modest amount.
- Don’t repeat often. Watch the plant and, if you feed with peels regularly, the soil pH.
Composting Banana Peels
Pavlis’s simplest advice is to add peels to the compost pile or let them decompose on the ground. Composting with other materials also helps make up for the low nitrogen. In a 2025 study by Msuya, Kitundu and Katima, banana peels and watermelon rinds were composted for 37 days at three ratios. The 1:2 peel-to-rind compost, with 5.87% potassium, gave the best growth of spiny amaranth, but the authors note that additional phosphorus and nitrogen are needed for optimal growth.
Practical tips: chop peels so they break down faster, mix them with brown material such as dry leaves or shredded cardboard so the pile doesn’t turn slimy, and use the finished compost as a top-dressing or in a repotting mix. Our guide on how to compost at home covers the basics.
Which Plants It Suits
Because peels supply potassium rather than nitrogen, they make most sense as a small extra for flowering and fruiting plants, such as tomatoes and peppers in containers, and flowering houseplants like anthurium. Foliage plants such as monstera still need a regular balanced feed.
Skip it for seedlings, plants already showing nitrogen deficiency (pale new growth), and carnivorous plants, which shouldn’t be fertilized through the soil. For choosing a main fertilizer, see our synthetic vs organic fertilizer guide.
Safety Notes: pH, Pests and Pets
- pH: the Wazir trial soil ended up at pH 8.98. Most houseplants prefer slightly acidic to neutral mix, so use small amounts and avoid heavy use on acid-loving plants.
- Pests: fresh peels and peel water attract fruit flies and fungus gnats. Dried powder worked into the soil, or finished compost, is cleaner.
- Pets: keep the jar of dried powder out of reach, and mix powder into the soil rather than leaving it on top where pets may dig. Check our cat-safe plants guide for the plants themselves.
For more on soil and feeding, see our guides to potassium silicate. For more on composting, see our guides to compost tumblers.
Frequently Asked Questions
What is the NPK of banana peels?
About 0.6-0.4-11.5 for dried peel and 0.1-0.1-2.3 for fresh peel, according to Pavlis. The 0-25-42 figure online is not realistic.
Is banana peel water good for plants?
It adds a little potassium and not much else (Pavlis). Use it fresh if you make it; drying or composting peels gets more out of them.
How do you make banana peel fertilizer?
Dry the peels until brittle, grind them into a powder and mix a small amount into the soil, or chop them and add them to compost.
How long does banana peel fertilizer take to work?
Slowly. In the Wazir trial, powder was mixed into soil 60 days before sowing to let it break down, and El Barnossi found two months of decomposition in soil worked best.
Can banana peels replace fertilizer?
No. They supply potassium but very little nitrogen, so pair them with a balanced or nitrogen-rich feed.
Sources
- Pavlis, R. Garden Myths: Banana Peels in the Garden
- Hikal, W. M. et al. (2022). Banana Peels: A Waste Treasure for Human Being. Evidence-Based Complementary and Alternative Medicine
- Khanyile, N. et al. (2024). Preparation of Biofertilizers from Banana Peels: Their Impact on Soil and Crop Enhancement. Agriculture 14(11): 1894
- Msuya, N., Kitundu, M. P. and Katima, Z. (2025). Production of Potassium-Rich Biofertilizer from Composted Banana Peels and Watermelon Rinds. Tanzania Journal of Engineering and Technology 44(1)