Onion skins are far too valuable to throw away! They are rich in potassium, calcium, magnesium, and iron, as well as sulfur compounds and antioxidants (such as quercetin).
In the garden or on the balcony, they solve one major problem in particular: nutrient deficiencies (recognizable by yellowing leaves) and troublesome pests like aphids or spider mites.
You can easily make a natural, free fertilizer and plant protection from the skins:
The method: Onion skin decoction
- Collect the skins: Store them in a dry place.
Collect the dry, papery outer layers of onions (and garlic). Make sure they are completely dry and free of mold.
- Prepare with water: Let it steep for 24 hours.
Place a large handful of onion skins in a container and pour one liter of water over them. Let the mixture steep in a cool place for at least 24 hours. (Quicker method: Pour boiling water over it and let it steep for 30 minutes.)
- Strain: Compost the peels.
Pour the liquid through a sieve or a cloth. The golden-brown onion brew is now ready to use. You can safely add the old peels to your compost.
- Use: Water or spray.
As fertilizer: Use the undiluted brew every two weeks as watering water to strengthen root growth.
As pest control: Pour the brew into a spray bottle and spray the upper and lower sides of affected plants.
Why it works: The sulfur in the brew repels sap-sucking insects like aphids, while the potassium strengthens plant cell walls and makes them more resistant to fungal diseases. A perfect, chemical-free all-rounder for houseplants and garden plants!