How to Use Coffee Grounds in Your Garden

By Christine Hennessey

My morning cup of coffee—brewed strong with a splash of almond milk—is an essential part of my day. And that same cup can give my garden a boost, too.

Used coffee grounds offer many benefits to plants, flowers, and vegetables—improving water retention, drainage, and soil aeration are at the top of that list. Coffee grounds also allow certain beneficial microorganisms to thrive and attract earthworms, which are a garden’s best friend.

How to add used coffee grounds to your garden

Always begin with damp—not wet—coffee grounds to prevent drying out your soil. Here are four ways to use coffee grounds in your garden soil.

  1. Using a spade or your hand, work the used coffee grounds into the soil around your plants, about six to eight inches deep.
  2. Use coffee grounds as mulch around your plants. Spread the used grounds directly on the soil, then cover with leaves or mulch.
  3. Make coffee ground “tea” by adding two cups of used coffee grounds to a five-gallon bucket of water. Let it seep for a few hours, then use as a liquid fertilizer in your garden.  
  4. Do you have leftover brew in your pot? Once the coffee has cooled to room temperature, add 1.5 cups of water for each cup of coffee, then pour into the soil around your plants as you would with regular water. Use this diluted mixture no more than once per week.

The benefits of coffee grounds

Because coffee is acidic, many people believe that adding grounds to your garden will increase the pH level of your soil, but this is a myth—only fresh coffee is acidic. Once it’s been used, most of the acidity ends up in your cup. The grounds are pH neutral, clocking in at about 6.5.

While used coffee grounds won’t alter the pH level of your soil, they do enrich it in other ways. Grounds are about 1.45% nitrogen and contain trace minerals, including magnesium, potassium, phosphorous, and calcium, which are released as they break down. This is good news for plants that do well in nitrogen-rich soil, such as spinach, corn, blueberries, roses, rhododendrons, and azaleas. Tomatoes thrive on nitrogen and particularly enjoy coffee grounds.

Plants should consume coffee in moderation. Don’t use more than six pounds of grounds for every 100 square feet. If the leaves of your plants are turning yellow, you’ve oversaturated and it’s time to cut back.

How to store coffee grounds

If you end up with too many coffee grounds, you can store them for later use as long as you dry them out first. This keeps them from decomposing or growing mold.

Simply spread the used coffee grounds in an even layer on a cookie sheet and place them in a warm oven to dry out. If it’s a hot day, you can also put the cookie sheet in a sunny spot outside or in a window. Once dry, store the grounds in a sealed container and keep them in a cool place until you’re ready to apply them to your garden.

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