Coffee and Soil Are More Compatible Than You Might Think
Forget about oil or electricity: coffee beans power the world. The world collectively consumes 2 billion cups of coffee each day, and one in two Americans depend on its bitter energy to get through the day. Regardless of where you buy your coffee— a cup of strong black from the local bodega, a fancy latté festooned with foam art, the instant kind at the Dollar Store— it’s safe to assume that those beans endured a long journey to get to your cup. After all, every drop begins with Coffea, a genus of plants that produces the fruit we know as coffee beans. Most people know and love coffee for its caffeine, but the beans don’t just benefit humans: our gardens can get a boost, too.
Because they are tropical plants, coffee trees and shrubs usually have a growing region restricted to the jungles of Brazil, Colombia, Vietnam, and Indonesia, where they thrive some of the most nutrient-dense soil on Earth. The beans are rich in essential oils, fats, and cellulose, as well as structural proteins, protective chemicals known as phenols, and other beneficial nutrients. During the brewing process, coffee is extracted from the beans by water, leaving behind the “grounds” most people throw in the trash without a second thought. That’s the million-dollar-mistake: all of the aforementioned compounds are hydrophobic, so they’re retained in the grounds after brewing. In other words, coffee grounds are perfect for your compost pile.
Just like eggshells, orange peels or carrot tops, coffee grounds are considered “green compost”– but the compound’s reputation is not entirely pristine. Perhaps due to the drink’s tendency to sour the stomach, many gardeners regard coffee grounds as a much too acidic (and thus potentially harmful) addition to a pH-sensitive plot. But while pH levels will undoubtedly change over time, coffee grounds actually tend to keep compost at a neutral pH. (They’re packed with nitrogen, but don’t rely on them as your sole fertilizer.)
“Coffee beans are rich in essential oils, fats, and cellulose, as well as structural proteins, protective chemicals known as phenols, and other soil-enhancing nutrients.”
Scientists have made great strides in cracking the coffee code, uncovering several purported defensive and synergic benefits over the past decade. In a 2009 article for MasterGardener, horticultural expert Dr. Linda Chalker-Scott linked coffee beans to disease suppression in a variety of crops (specifically: beans, cucumbers, and spinach) that were all grown under controlled conditions. Her report also uncovered synergy with other species: improved germination in sugar beets, bumper crops of cabbage and soybeans. As with people, there are plants who don’t take well to java: experts at Oregon State University warn of lowered germination and stunted growth in lettuce seeds fertilized with coffee grounds, for example.
Whether you’re a seasoned rooftop gardener or a 9-to-5’er with a raised bed and no time for composting, the process of “coffee gardening” is surprisingly simple and stress-free. Cafés are desperate to get rid of their excess grounds, so the next time you’re at your favorite spot, ask the barista if they’ve got grounds to give away: almost 100 percent of the time, the answer will be yes. Starbucks is another good bet; many locations feature baskets full of bagged coffee grounds, complete with instructions for use. When it’s time to plant, just fold the grounds into your preferred soil. Should you choose to compost, make sure to supplement the dark, fragrant goodness with plenty of bulk– like leaves, grass clippings, and newspaper strips. When everything’s planted, relax and take a coffee break— you just gave one to your plants, after all.
