Twelve years ago Starbucks began giving spent coffee grounds to local gardeners in Seattle on a first-come come, first-serve basis. The initiative was one way to fulfill the corporate mission of active environmental responsibility in communities in which they do business. The local stewardship spread quickly to all Starbucks locations across North America.
Coffee grounds are a significant percentage and the heaviest part of the waste stream at Starbucks. The Grounds for Your Garden initiative targets waste reduction and community involvement. The complementary spent grounds are packaged in recycled bags with a sticker attached giving tips for use directly in the garden, worm bin, and compost pile. When gardeners, schools, parks, and nurseries use the grounds for compost and mulch, a valuable organic resource is returned to the earth.
The Language of Composting
In the language of composting, coffee grounds are considered ‘green’ nitrogen sources like grass clippings, vegetable scraps, and animal manures. The ‘brown’ components in compost are dead leaves, straw, sawdust, and hardwood ashes which contribute carbon.
Organic materials are composed of a carbon-nitrogen ratio. The carbon-nitrogen ratio in coffee grounds is 20:1 indicating the grounds are a good nitrogen source.
An analysis of the grounds reveals they contain the basic three nutrients of nitrogen, phosphorus, and potassium, aka N-P-K, for plant growth. The elements magnesium, copper, calcium, and sulfur are also found in coffee grounds.
Why Use the Grounds
Gardeners extol the many benefits of the grounds:
- When mixed with brown materials in the compost bin, grounds generate heat to speed up decomposition.
- Coffee grounds absorb and retain moisture enabling them to affect the soil's texture.
- The acidity of the grounds can be balanced with lime and /or hardwood ashes. However, many gardeners mulch acid loving plants like azaleas, camellias and blueberries with spent grounds. Acidic grounds keep your hydrangeas blue too.
- Tomato growers sidedress their plants for the nitrogen boost, added calcium and to suppress late blight.
- Roses and vegetable beds benefit from the java jolt as well.
- Grounds sprinkled on lawns contribute nitrogen, the greening nutrient for actively growing lawns.
- Hosta and lily growers find that slugs and snails are repelled by the grounds.
- Earthworms enjoy a coffee klatch in a vermicompost bin and in no time their java castings perk-up the garden.
- Outdoor container plants and indoor houseplants respond favorably when grounds are worked into the soil or are offered as a liquid plant fertilizer. Dilute the grounds in water to form an amber cordial. Similarly, rather than pouring leftover coffee down the drain, feed the elixir to your plants instead.
Precautions
Applying coffee grounds directly to the soil may cause some problems. Since coffee grounds are acidic, composting the grounds with kitchen scraps, yard debris and wood ashes forms a less acidic product.
If wet grounds are worked into the soil or placed directly on the surface, they may form an unwanted mildew mat. Wet grounds may be dried in the oven at a low temperature.
Take advantage of the free resource to brew a compost to energize your garden year-round.
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