Fertilize Your Garden With A Common Leftover Ingredient From Your Kitchen

We cry when someone cuts onions. Not because the sharp acids are hitting our eyes, but because the peel is most likely going to waste. That thin outer shell that gets sent to the landfills is filled with nutrients for your plants. Onion peel is one of the many food scraps that can be used to fertilize your garden. With water and a handful of peels you can make an inexpensive, chemical-free liquid fertilizer that can help your plants grow and fight diseases.

Onions (Allium cepa) contain calcium, magnesium, phosphorus, and potassium — nutrients plants need and are often found in commercial fertilizers. A 2022 study published in the International Journal of Scientific Development and Research found using onion peel water as fertilizer promoted flowering, increased plant growth, and decreased bacterial and pathogenic diseases and a 2024 research study published in HortScience also showed the homemade fertilizer boosted root growth and increased soil fertility. The mixture was used on a variety of plant species, from vegetable crops like lettuce and bok choy to flowering chrysanthemums. So, regardless of what you're growing, onion peel fertilizer might be just what your plants need.

The peel from white, yellow, and red onions are perfect for this DIY fertilizer tea you can make to nourish your garden and potted plants. First, add a few handful of onion peels to a large container and pour in 34 ounces (or 4 ¼ cups) of water. Cover the container and place it in a dark area for 24 to 48 hours. You'll know it's ready to use when the liquid turns a reddish brown color. Then, strain the solution to remove any remaining onion peels. These solid pieces can be thrown into the compost bin while the onion-steeped water is now your liquid fertilizer.

The liquid fertilizer is concentrated, so you'll need to dilute it before using it as plant feed. Mix roughly 7 to 10 ounces (or around 1 cup) of the onion peel concentrate for every 34 ounces of water. With the diluted fertilizer, you can use it up to once a week to water the soil or spray it directly on to the plants. The mixture should last for about a month stored in a cool dark place. This is a simple onion hack to use in your garden, and gives what would normally end up in the trash a new life.