Your Peace Lilies Will Thrive With The Help Of An Unexpected Leftover Kitchen Scrap

Peace lilies (Spathiphyllum wallisii) are a great plant with gorgeous white blooms to have around either indoors or outdoors, but you'll need to give them some tender loving care. One of the tricks that could help them thrive is to add used coffee grounds to their soil. Peace lilies are one of the plants that love coffee grounds. Coffee grounds contain nitrogen, carbon, magnesium, potassium, and calcium, which can strengthen the plant's health and serve as a natural fertilizer.

A 2024 study in the Plant Physiology and Biochemistry journal notes that spent coffee grounds (SCG in the study) can do a great job of improving soil and adding nutrients. However, the study also notes that recently used coffee grounds, in particular, may contain some toxic compounds that could have adverse effects. If applying coffee grounds to peace lilies or another plant, do so with caution and pay attention to the houseplant overall as time goes on. Before adding coffee grounds to the soil, know its current condition — consider a soil test first.

If you also use a fertilizer, adding fresh coffee grounds to the soil may lower the pH too much and it may become too acidic. To avoid this, stick to used coffee grounds or compost them first, and take the plant's entire care routine into consideration. Used coffee grounds may serve as a fertilizer thanks to their nitrogen and nutrient content, but if needed, the acidity of fresh coffee grounds may also help alter the pH of the soil — peace lilies prefer slightly acidic soil with a pH between 5.5 and 6.5. But again, be sure to do some testing first if you're using coffee grounds to adjust pH levels.

There are several ways to use coffee grounds for peace lilies, but first, make sure you're using black coffee grounds that are organic or unflavored — they shouldn't have additives or extra ingredients. Stick to used coffee grounds since these will be less acidic and have less caffeine.

One of the best ways to use the grounds is to apply them directly to the soil as a mulch, sprinkling them around the base of the plant. Create a thin layer and spread them evenly while leaving some room, preventing direct contact with the stem. Alternatively, spread coffee grounds into the soil's top layer using a hand trowel. Another option is to make a liquid fertilizer with the grounds. Combine a teaspoon of coffee grounds with a gallon of water and let the solution sit for a few days. Then, strain the liquid with a cheesecloth. Use the strained liquid to water and fertilize your peace lily. Finally, consider using coffee grounds as part of a home compost. Simply add them to the compost pile along with your normal home compost items and let them decompose. 

Remember that whenever you use spent coffee grounds on your peace lilies, water thoroughly afterward. Also, pay attention to your houseplant's condition. Take note if your peace lilies get curly leaves, start yellowing, or if there are other signs of trouble. Do everything you can to keep your peace lilies healthy and growing their best — ensure they stay between 65 and 80 degrees Fahrenheit, keep the soil moist without overdoing it, and ensure they have bright, indirect light.