Happy National Joe Day! For many of us, having a cup (or five) of joe is an essential part of our morning routines. Coffee helps allay drowsiness, grumpiness, and laziness; it calls us to action and fuels the fires of productivity. But, beyond its usefulness as a caffeinated beverage, coffee is also a valuable gardening resource. Gardeners have long been using coffee grounds as a component in compost, fertilizer, and mulch. Some even suggest that coffee grounds can deter pests like ants from damaging crops and flowers. If you have a lot of leftover coffee grounds and want to try putting them to use in the garden, here are some tips of where to start:
Coffee and Compost
In general, coffee grounds contain a healthy amount of nitrogen, potassium, and magnesium, plus small amounts of other nutrients than can benefit plant growth. Quality and nutrient density varies depending on the type of coffee, and so gardeners often chose to use high-quality, organic coffee for their plants rather than generic brands.
Incorporating coffee grounds into a fertilizer or compost pile is easy and normally requires little preparation. You can sprinkle clean grounds right on top of existing soil (and mix well) or on top of a compost pile. For composting purposes, coffee is considered a “green” component, meaning it must be balanced out with sufficient “brown” components, like dried leaves and wood scraps. Using coffee this way is widely regarded as safe and effective, and it is much more useful than throwing pounds of coffee grounds into the trash every week! For more on composting, see our how-to guide.
Coffee and Mulch
Inundating plants with large quantities of coffee grounds can do more harm than good. Coffee grounds are typically highly acidic and can cause mold outbreaks if used in excess. However, a light smattering of grounds mixed with other organic material can make a great base for mulch. Start by mixing a handful of coffee grounds into a bucket of compost or leaf mold, and then spread the mixture liberally over plant beds. The nutrient-rich coffee grounds should mix well with the other material, and provide a healthful covering for plants. If your plants are highly sensitive to acid, and you’re worried adding acidic coffee grounds to your soil might hurt them, consider mixing a cup of agricultural lime or hardwood ashes into your grinds before adding them to compost/leaf mold.
For gardeners whose soils are highly alkaline (low in acid), adding coffee grounds directly to the soil could help neutralize it without creating any adverse effects.
On this National Joe Day, give thanks to America’s favorite caffeinated beverage and the various ways it is used for our betterment—including in America’s gardens!