We are frequently asked if coffee grounds can be used in a garden. The short answer is yes, coffee grounds can be used in garden soil!
Coffee grounds contain some major nutrients (nitrogen, phosphorus, and potassium) as well as some micronutrients, so put them to work in your garden. Allow them to dry and then spread them around the base of plants.
Apply no more than one-half inch of coffee grounds when putting fresh coffee grounds directly to the ground as mulch. Because coffee grounds are finely textured and easily compacted, thick layers of coffee grounds as mulch can act as a barrier to moisture and air movement in soils.
So if you are using coffee grounds as a “dressing” for specific plants or trees, apply the grounds in a thin layer or work into the top layer of the soil.
University of Wyoming has more information:
http://www.uwyo.edu/barnbackyard/_files/documents/magazine/2017/summer/plantsperk0717.pdf
Article by Gail Reynolds, Middlesex County Master Gardener Coordinator