Q. Are coffee grounds a good fertilizer for outdoor plants?
Coffee grounds, direct or composted, are a readily available fertilizer. The grounds are are a source of nitrogen as well as magnesium, calcium, potassium, and other trace minerals. They are particularly good for acid-loving plants such as tomatoes, roses, azaleas, blueberries, evergreens, camellias, avocados, and some fruit trees. However, you can use coffee grounds for most plants as the acid level is not as high as you would think--a substantial amount of the ‘acid’ is cooked out of the coffee and drunk. Just reduce the amount used for other plants.
- Top Dressing: Grounds can be directly applied as a top dressing to nitrogen-loving plants such as azaleas, roses, lettuces and most perennials.
- Compost: Coffee grounds and filters can be added to your compost pile. The grounds act as a green material, high in nitrogen. Combined with dry, brown material, coffee helps create a rich environment for the compost micro and macro organisms to break down the waste.
- "Tea": Add two cups of used coffee grounds to a five-gallon bucket of water. Let the "tea" steep for a few hours or overnight. Use as a liquid fertilizer.
- Vermiculture: The grounds can also be used in worm bins along with other household waste to create vermicompost (compost made by red worms).
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service