Coffee as Plant Food

Used coffee grounds make an effective and fast-acting fertilizer for plants and vegetables. Recycling spent grounds is easy, cheap, good for the environment and has the added bonus of being a natural insect repellent. This DIY plant food eliminates the need for adding harsh chemicals to your garden.

How to Make Coffee Grounds Fertilizer

Dilute 2-3 cups of coffee grounds in 5 gallons of water to make a liquid plant food that gives an instant nitrogen boost to your houseplants or outdoor garden. For slow-release nitrogen, you can sprinkle used coffee grounds directly onto the soil around the base of your plants. When the plants are watered, the nutrients will slowly leach into the soil and the plants' roots.

The Science

Strawberry in garden image by Olga Chernetskaya from Fotolia.com

Coffee grounds contain 1.45 percent nitrogen, but they also contain tannic acids, calcium, magnesium, potassium and other minerals that help plants grow. Since they are acidic, coffee grounds work especially well as fertilizer for acid-loving plants such as blueberries, strawberries, gardenias, azaleas, hydrangeas, magnolias, ferns and rhododendrons. Oak, pine, spruce and fir trees also love acidic soil. Spent ground coffee has a pH level of about 4.0, so add your diluted grounds no more than twice a week. (Most edible plants like acidic soil, but some plants, such as eucalyptus, ficus, chrysanthemum and clematis, prefer alkaline soil).

For Your Garden or Compost Bin

For a more powerful fertilizer, mix your diluted coffee grounds with finely crushed eggshells, which will provide much-needed phosphorus and calcium to your soil. Worms, whether in your garden or your compost bin, love coffee. (If you compost, you can add used grounds directly to your pile without diluting them.)

Coffee Grounds for Pest Control

Coffee is not just great plant food, it is also an easy pest-repellent for your garden or vegetable plants. Slugs and snails are some of the most common problems in the garden, as they love to feast on plants and seedlings. Used coffee grounds are a natural and easy way to deter these slimy creatures from putting too many holes in your plants. You can use coffee grounds to mulch around slug-loving plants like marigolds, strawberries and lettuce.

Recycling Coffee Grounds

If you are not a coffee drinker, you can ask your local coffee shop if they will give you their spent coffee grounds. Starbucks gives out their used coffee grounds for free for gardening and composting--just ask at your local retail location.