Coffee grounds are a versatile material that can be repurposed and upcycled in many ways. One of the best uses for spent coffee grounds is to turn them into fertilizer for your garden and houseplants. Upcycling used coffee grounds into fertilizer is an easy, eco-friendly way to reduce waste while enhancing your soil and plants.
Why Use Coffee Grounds as Fertilizer
Coffee grounds contain essential nutrients that are beneficial for plant growth and soil health. Here are some key reasons why repurposing coffee grounds as fertilizer is advantageous:
Coffee grounds are rich in nitrogen, one of the macro-nutrients that plants need to thrive. The nitrogen in coffee fertilizer promotes healthy green growth and leaf development. This makes coffee an ideal fertilizer for leafy greens and vegetables.
Adds Organic Matter
The organic compounds in coffee grounds enhance soil structure and water retention. As the grounds break down, they improve drainage in dense, heavy soils. In sandy soils, the organic material helps retain moisture and nutrients that would otherwise leach out. Over time, coffee grounds can make any soil more nutrient-rich and better structured.
May Suppress Harmful Fungi
Some research indicates that using coffee grounds as mulch may help suppress the growth of harmful fungal diseases that can damage plants. The caffeine and other compounds in coffee are believed to limit fungi like Verticillium wilt.
Sprinkling dry used coffee grounds around plants may help deter slugs, snails, and ants. These creatures dislike crawling over the gritty, rough texture of coffee grounds. The caffeine may also repel certain garden pests.
Rather than sending tons of used coffee grounds to landfills each year, repurposing them as fertilizer gives them a second life. Upcycling organic waste like coffee reduces unnecessary waste and your carbon footprint.
How to Apply Used Coffee Grounds as Fertilizer
It’s easy to start using your leftover coffee grounds to nourish plants. Here are some simple techniques for using spent coffee grounds as fertilizer:
Mix Into Soil Directly
One option is to sprinkle dry used coffee grounds in your garden beds or potting soil as you plant. Mixing 1-2 tablespoons per square foot into the top few inches of soil provides plants with a nutrient boost. Over time, the grounds will continue releasing nitrogen as they decompose.
Add to Compost
You can add coffee grounds to any compost pile, bin, or worm bin. The grounds provide a source of nitrogen and carbon. Composting the grounds first allows the nutrients to break down into a more stable form before applying to plantings.
Fertilize Potted Plants
For houseplants and potted patio plants, used coffee grounds can be blended into the potting mix. Once a month, sprinkle 1 teaspoon of grounds per inch of container diameter onto the soil surface, then water in well. The nutrients will feed plants with each watering.
Make Coffee Ground “Tea”
Soaking used coffee grounds in water creates a mild liquid fertilizer or compost “tea.” Let the grounds steep in a bucket of water for a day or two. The resulting coffee ground tea provides a quick nitrogen boost when poured onto plants or used to water them.
Sprinkle dry used coffee grounds around plants as mulch. Apply a thin layer about 1/4-inch deep around the base of plants. Over time, rain and irrigation will help dissolve nutrients out of the coffee grounds. The grounds will also retain moisture in the root zone.
Add to Worm Bin
Worm composting systems thrive when you add used coffee grounds. The worms help break down the grounds into rich vermicompost. Feed worms about 1 handful of fresh grounds per square foot surface area every week. Avoid overloading, as excess acids can harm worms.
No matter which fertilizing method you choose, distributing the grounds thinly and evenly is important. Too many grounds piled in one place can provide more nitrogen than plants can handle.
Best Plants to Fertilize with Used Coffee Grounds
While most plants can benefit from used coffee grounds, some types truly thrive with the addition of coffee fertilizer. Plants that especially appreciate nitrogen-rich coffee grounds include:
- Vegetable crops: Leafy greens, tomatoes, carrots, peppers, radishes
- Fruiting plants: Citrus trees, berries, melons, squash
- Herbs: Rosemary, lavender, mint, parsley, cilantro
- Flowers: Azaleas, camellias, roses, hydrangeas, gardienas
- Trees and shrubs: Evergreens, hollies, magnolias, jasmine
Coffee grounds may be less suitable for beans, peas, corn, and other plants prone to fungal issues. Observe how your individual plants respond.
Plants that need acidic soil tend to appreciate used coffee grounds. Azaleas, blueberries, evergreens and other acid-lovers benefit from the pH-lowering effect grounds provide as they break down.
Tips for Using Coffee Grounds as Fertilizer
Follow these tips to safely and effectively use spent coffee grounds as fertilizer:
- Allow wet coffee grounds to dry fully before placing around plants to avoid mold growth.
- Stir grounds into soil and composts thoroughly so they contact roots and microbes.
- Alternate coffee fertilizer with other organic fertilizers like compost or manure.
- Rinse off fresh grounds from foliage to prevent burning leaves.
- Monitor nitrogen levels to avoid overly “hot” soil from excess grounds.
- Limit coffee fertilizer for seedlings, which need less concentrated nutrients.
- Consider composting or worm composting kitchen scraps along with grounds.
With a little work, those piles of used coffee grounds can nurture lush, healthy plants instead of taking up space in landfills. Follow the right techniques, and you’ll quickly start reaping the many benefits of upcycling coffee grounds into fertilizer for your garden.