“Organic matter needs to be decomposed first (through composting) to make individual nutrients they hold available to plants,” Halleck says. Ironically enough, attempting to take a shortcut and place used grounds directly on soil can actually starve your plant of nitrogen in the long run. “As fresh organic matter begins to decompose through the decomposition cycle,” Halleck explains, “nitrogen can be immobilized by microbes in the soil, which can lead to a nitrogen deficiency in your plants.” Soil researchers at the University of Melbourne1 demonstrated this in the lab when they directly applied spent coffee to the soil of broccoli, leek, radish, viola, and sunflowers. Though the grounds seemed to increase the amount of water the soil could hold, they ultimately hampered growth for all five types of plants. Uncomposted kitchen scraps of all kinds can also create the conditions for mold as well as attract unwelcome fungus, bacteria, and fungus gnats to your plant, adds Halleck. Jonathan Russell-Anelli, Ph.D., a senior lecturer in Cornell’s School of Integrative Plant Science, also finds fault with most recommendations to use kitchen scraps as fertilizers. “Kitchen recipes are generally based on garden folklore and can quickly damage gardens if not understood and used correctly,” he tells mbg. Russell-Anelli also vouches for this quick-release fertilizer method. Make your brew by allowing your finished compost to “steep” in water and sugar. The finished product will deliver the valuable components of compost in a liquid form that can be added directly to your plant’s soil. Emma received her B.A. in Environmental Science & Policy with a specialty in environmental communications from Duke University. In addition to penning over 1,000 mbg articles on topics from the water crisis in California to the rise of urban beekeeping, her work has appeared on Grist, Bloomberg News, Bustle, and Forbes. She’s spoken about the intersection of self-care and sustainability on podcasts and live events alongside environmental thought leaders like Marci Zaroff, Gay Browne, and Summer Rayne Oakes.
