Organic Plant Care

A lot of people don’t realize that onion water is an inexpensive way to boost plant performance. Onions are an excellent source of potassium. They are also rich in calcium, iron, magnesium, copper, vitamin C, and folate. The skins and peels make great additions to a compost pile. But those minerals and supplements can be easily extracted by soaking the skins and ends in water creating a super nutritious tonic–onion water.

Benefits of Onion Water

Potassium. Onion’s high potassium score makes it ideal as an organic fertilizer. Commercial fertilizers advertise an N-P-K score on their packaging. The N stands for Nitrogen, P stands for Phosphorous, and K represents Potassium.

Nitrogen is essential for leaf growth and is a major component of chlorophyll. Organic planting media (potting soils, compost, manure) provide nitrogen. Phosphorus is essential to healthy roots and warding off disease. Phosphorus is essential in getting plants to fruit and flower. Potassium makes stems strong and boosts growth.

Pest Control. The strong onion smell seems to protect plants from some pests,

How to Prepare Onion Peel Fertilizer

Onion-based fertilizer is the result of mixing peels and unusable cuts of onions with water in any eco-friendly bin. I keep a quart-size plastic deli container next to my kitchen compost pail because it holds the 3-4 handfuls of peelings and, more importantly, it has a top to trap the onion smell. I fill the container with peels over one or two days, and then top it off with tap water. Allow the peels to percolate at room temperature for 24 hours before straining out the peels for the compost pile. The amber liquid left behind is now a ready-to-use organic fertilizer.

I keep a plastic drink dispenser as a “mother jar” of onion water in the garage during the growing season so I have an endless supply available for use.

The Best Ways to Use Onion Water Tonic

Using this tonic on your plants is no more difficult than watering. Dilute on part prepared tonic with 10 parts water. A little tonic goes a long way. It can be sprayed on plants or added to a watering can. Application is difficult to control in a hose-end sprayer, and often you’ll waste more of the tonic without getting the benefits.

I use onion water weekly on all my house plants, orchids, Christmas cactus plants, vegetable garden, and potted patio plants.

Plant Response to Onion Water

My garden is alive with hundreds of plants. The 60 plus orchids are definitely the starring artists. But there is always something in bloom in the garden. Several plants were handed down to me from my parents or friends who moved. All of them can benefit from onion water fertilizer.


    1. Hi Mary. I actually use onion water on all my plants once a month. On my orchids and tomatoes I alternate watering with a mixture of 1 teaspoon Epson salts to 1 gallon of water.

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