As a daily coffee drinker and long-time advocate of composting, coffee grounds generated in my kitchen go into the compost pile. But, apparently, gardeners are increasingly using coffee grounds, collected from coffee shops, as mulch.
This is not a practice I had considered until I read Linda Chalker-Scott’s peer-reviewed fact sheets on this topic. As one of The Garden Professors, Linda is a huge proponent of science-based gardening information.
Her newest fact sheet, Using Coffee Grounds in Gardens and Landscapes, provides valuable advice for home gardeners. I strongly advise you follow the link and read the entire fact sheet, but here are a few of her points:
- fresh or composted coffee grounds can be safely used as mulch, but no deeper than a 1/2″ layer and not on seed-starting beds as the grounds tend to reduce germination.
- to prevent the grounds from compacting and limiting moisture to the soil, they should be covered with a coarse mulch of organic material.
- coffee grounds are not always acidic and, therefore, should not be used to alter soil pH.
- only composted coffee grounds should be worked into the ground as a soil amendment.
- coffee grounds should compose of no more than 20% of the volume of a compost pile.
Want to read more of Chalker-Scott’s science-based advice for gardeners? Check out The Informed Gardener. It is easy reading and pares scientific research against gardening and landscaping myths.