QUESTION: Are coffee grounds good for herbs? I was thinking that maybe I could add them to my herb containers. – Lisa A
ANSWER: To put it bluntly, no—coffee grounds are not good for herbs, and they should be used with care around the plants that do benefit from them. It’s true that generations of gardeners have amended their soil with coffee grounds or sprinkled them around plants because they believe the nitrogen in coffee grounds helps plants to flourish. Because coffee has been used this way so long, you’ll see it recommended as a fertilizer, mulch, and composting ingredient all over the web. However, coffee grounds are extremely acidic, so they’re best used around plants that thrive in acidic soil, like blueberries, rhododendrons and azaleas — if you use them at all. Take care if you choose to use them this way, though, and use a light hand, because coffee is so acidic that the pH level of some grounds have tested as even more acidic than acid-loving plants can stand.