Q. I am interested in using the coffee grounds that Starbucks provides free to gardeners to add nutrients to the soil. However, I am unsure how much to add to the soil and wonder which perennials would benefit from these grounds. Thank you!
Andover, Massachusetts
A. Thanks for your question about using coffee grounds in your garden. I recently wrote about this on my blog. Here’s what I found out:
Used coffee grounds are a good soil amendment but, contrary to popular belief, grounds don’t make a good fertilizer when used alone. The best use of used coffee grounds is to add them to the compost bin as another source of “green.” The researchers at the Oregon State University Extension Service say when coffee grounds are used as a soil amendment, “keep them damp and add some nitrogen fertilizer when you do this.” Apparently the grounds feed microbes in the soil, which depletes nitrogen and needs to be replaced.
The experts also say, if grounds are used on the soil surface, cover them with leaves or bark mulch.
Another tip when using coffee grounds is to side-dress plants with no more than 1-inch of grounds at a time and to wait until the grounds decompose before adding more.
Starbucks provides information on how to use the grounds in the garden, such as applying the grounds “directly as a top dressing to acid-loving plants like blueberries, hydrangeas, and azaleas.”
Regards,
Jodi Torpey, master gardener
www.WesternGardeners.com
