Many people throw used coffee grounds out with the trash. But coffee can be a very good organic fertilizer for your garden. Whether you compost used coffee grounds with the rest of your organic kitchen wastes or apply them directly to your garden soil, coffee can add nitrogen and organic material that will help your plants grow.
Used coffee grounds contain about 2 percent nitrogen by volume. Whether the coffee goes directly in the garden or as part of compost, the nitrogen in it encourages green leafy plant growth. In compost, this source of nitrogen will feed the bacteria that convert the other materials into usable organic nutrients.
Used coffee grounds have a neutral acidity. The acids in coffee are water soluble and are washed out of the grounds into the coffee. Adding used coffee grounds to your soil or compost will not raise or lower your soil's acidity, unless the soil is unusually acid or alkaline.
A common way to use coffee as fertilizer is to compost the used grounds. You can include any paper filters used to brew the coffee. After several weeks of composting, the coffee will turn into rich, black compost with high levels of organic matter.
If you directly apply the coffee grounds to the soil, you have a couple of options. One is to spread the coffee on top of the soil and work it in with hand tools or your hands. Another is to spread the coffee on top of the soil and add mulch to hold moisture around the coffee and soil. Coffee alone spread on top of the soil can repel water like dried peat moss.
Sources of Used Coffee Grounds
If you have large gardens, consider locating a source of coffee grounds. Many coffee shops are happy to give coffee grounds to neighbors and nearby residents. By giving you the used coffee, they reduce their landfill waste and help garden plants. Talk with a number of coffee shops to find the right amount of coffee for your gardening needs. Some shops may not give you the coffee because too many other people have beaten you to it.