Adding Coffee Grounds to the Garden
Put coffee grounds and filters to work improving your garden’s beauty and productivity.
Recycle these morning discards in your compost pile or worm bin. The worms and microorganisms will break them down into wonderful compost. Or occasionally sprinkle the grounds on the soil surface of your indoor and outdoor container and in-ground gardens.
Avoid adding large amounts at one time. This can temporarily tie up soil nutrients, making them unavailable to the plant. Incorporate larger amounts into the soil, along with shredded leaves in fall or add them to your compost pile. Once they decompose these nutrients will be available for the plants.
Although coffee grounds are acidic, they have a minimal effect on the soil pH. They do, however, contain allelopathic chemicals that can inhibit growth of certain susceptible plants and prevent some seeds from sprouting. Once the coffee grounds fully decompose this is not a concern.
A bit more information: There is some evidence that decomposing coffee grounds help suppress some diseases in certain plants. Some researchers believe certain substances released during decomposition may be responsible for damaging sensitive plants. When composting, use only 10 to 20% coffee grounds by total volume for optimal benefit. Over 30% can be detrimental to the garden and plants.