Are Coffee Grounds Acidic?
Magnolia trees (Magnolia spp.), generally, are among the plants that prefer a soil pH that is acidic. That is the reason why some folks who have a soil that is too alkaline are attracted to the idea of sprinkling coffee grounds on the earth around their magnolia trees. They have heard that coffee grounds are acidic, so they figure that they can acidify the soil in this way. And the concept makes sense to them because the coffee that we drink is highly acidic—something to which anyone who suffers from an upset stomach after drinking a cup of coffee can attest. But when we move the discussion from the realm of food and drink to that of gardening, it is not quite so simple. For one thing, we must break the matter down into two separate questions: Fresh coffee grounds are, in fact, acidic. Problem is, gardeners rarely have fresh ones in mind when asking this question because fresh coffee grounds have value in the kitchen. It would occur only to people who do not drink coffee to use fresh coffee grounds in the garden. By contrast, used coffee grounds are not very acidic; they are more or less neutral, pH-wise. Even if you are thinking of sprinkling fresh coffee grounds around your magnolia tree, you should have a soil pH test done first to try to find out whether your soil is acidic, alkaline, or has a neutral pH. If such a test indicates that your soil is way too alkaline, then, fine, use the fresh coffee grounds around your magnolia tree. Sprinkling fresh coffee grounds around such acid-loving plants will be helpful if the soil in which they are growing is currently too alkaline for them. An application of fertilizer with ammonium-N is another trick used to acidify the soil. But, otherwise, do not apply fresh coffee grounds directly on the earth around your magnolia tree. Further acidifying soil that is already acidic enough might be counterproductive.
Other Benefits of Coffee Grounds
So far, we have only discussed how coffee grounds affect soil pH, concluding that it is only the fresh ones that have an impact. Luckily, both fresh and used coffee grounds have other gardening benefits:
