Coffee is an environmentally friendly way to repel unwanted insects and animals in the garden. The smell of the coffee repels snails, slugs and ants. You may also have success using coffee grounds to repel mammals, including cats, rabbits and deer. Research published in September 2014 in the journal Science showed the caffeine in coffee plants evolved as a natural pest repellent.

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A slug crawls on a flowers stem.

Using Coffee As a Repellent

Coffee can help fertilize soil and repel pests. Coffee grounds contain nitrogen, phosphorus, potassium and other nutrients plants need. Sprinkle the coffee grounds around plants, or mix them into soil as you plant your garden. There isn't a perfect formula for how much coffee grounds to use, so you may need to try different quantities to determine how much works best in your garden. Don't put out large, wet clumps of grounds of more than 1/4 cup in one spot as this may develop mold.