What can we do with coffee grounds remaining from our daily pot of coffee? Spooning the grounds on top of the soil of potted houseplants is one of the handiest disposal methods. But are coffee grounds safe, beneficial or hazardous for houseplants?
Here are guidelines:
- Coffee grounds are an organic material that improves soil condition and can help prevent houseplant soil from becoming hard-packed.
- It would seem that coffee grounds would acidify soil, but tests have indicated that coffee grounds are neutral in pH. The acidity is leached out, percolating down into the coffee we drink. There might be a slight benefit to acid-loving plants, but the neutrality of coffee grounds won’t measurably acidify soil.
- As coffee grounds decompose, they release a small amount of nitrogen fertilizer, with an analysis of about 2%.
- Some research indicates that coffee grounds might inhibit damaging rot-type fungus from establishing in soil.
- How much coffee grounds can we safely add to houseplant soil? As with most things, it shouldn’t be overdone. The equivalent of a one-inch layer, accumulated per year, cultivated into the soil surface should be a safe, beneficial amount.
- What to do with extra coffee grounds when our houseplants have had enough? They’re great additions to the compost bin, or just dump them on the surface of gardens or flowerbeds. They improve soil structure, add a little fertilizer, and the scratchy texture of dry coffee grounds can help reduce slug damage around plants.
What about that half-cup of leftover cold coffee? Can we dump it on a plant? Yes, research has shown that liquid coffee can be poured on houseplants, in moderation of course. Besides nitrogen, coffee contains a little phosphorous and potassium. The acidity of liquid coffee would be appreciated by acid-loving plants like azalea. The acidity also helps neutralize the buildup of alkaline salts that accumulate from houseplant watering.
So go ahead and share a cup of coffee with your favorite houseplant. Happy Gardening!