I’ve heard that coffee grounds can be beneficial in the garden. What are the best ways to use them?
John Wilson, Bangor, MI
Working coffee grounds into the soil will improve its tilth, but do this sparingly unless you have acid-loving plants, like camellias and azaleas.
Photo/Illustration: Allison Starcher
Sharon Lovejoy, the author of Trowel & Error, who divides her time between Cambria, California, and South Bristol, Maine, replies: Our ancestors had it right. Waste not, want not—or as my elderly cousin, Margaret MacDonald, often preached, “A good Scotsman doesn’t waste anything.” And that includes coffee grounds. They’re pure gold for your garden, compost pile, and best of all, your worm bin (you do have one of those necessities, don’t you?). From my point of view, the invention of the garbage disposal was one of the worst moments in household and garden history. For every pound of “garbage” washed down the drain, we waste at least 8 gallons of precious water and compostable vegetable matter that could be put to good use in our gardens.
Some of my earliest memories include my grandfather dumping his morning pot of coffee grounds into the compost pile or onto his bountiful rose borders. According to scientists, coffee grounds have a carbon-to-nitrogen ratio of 20:1, which is what kept my grandfather’s compost pile active and healthy and his garden beds friable. Plus, his beds were always free of slugs and snails, since the creatures don’t seem to like the remnants of this rich brew.
I love the old Tennessee adage of “too much is not enough,” but in the case of coffee grounds, too much can be too much. Although coffee grounds can be added directly to the soil, I use them sparingly in most of my beds and borders (the exception is around my camellias and azaleas) so as to not raise acidity. I also take care to work them into the soil, since I’ve found that wet grounds on top of soil can develop into a thick mat of mold, something both unattractive and unhealthy.
I have the most success with coffee grounds when I use them in my covered worm bin. Of the many foods and clippings I offer my worms, the grounds top the popularity list and are among the first items to disappear. My theory is that grounds are worm friendly—perfect little worm-size mouthfuls that don’t require a lot of work, and like teenagers, worms will skip the food that requires lots of work and go for the easy meal. Within just three weeks (in spring, summer, and fall), the worms process the grounds and turn them out as clean, odorless castings, which are Mother Nature’s booster shots for the garden.
Successful people always are resourceful and gardeners are no exception. Don’t let the opportunity for freebie coffee grounds pass you by. Get courageous and ask your local coffee shop or restaurant to save some of their leftovers for you. Haul them home and alternate layers of grounds with leaves, twigs, corn husks, or straw in your compost pile. Within months, your coffee grounds will be ready to return to the earth, which is where all good garbage belongs.