When used as a plant fertilizer, coffee grounds can replenish the soil acidity that is often lost in potted and in-ground plants. Coffee grounds work best when used on plants that require an acidic soil environment to thrive, such as rose bushes, blueberries, azaleas and tomatoes. The nitrogen in coffee grounds also raises the temperature of the soil, which can kill weeds and curb pests. Coffee grounds can be converted into solid and liquid fertilizers.
Loosen the top layer of soil around the base of the plant with a gardening spade.
Sprinkle a handful or two of coffee grounds in the loose soil. Use the spade to turn over the dirt and mix in the grounds.
Water the plant to allow the nutrients from the coffee grounds to seep into the soil.
Repeat as frequently as once weekly.
Drop a handful of used coffee grounds into a 2-quart pitcher. Fill the pitcher the rest of the way with warm water. Set it in a cool place.
Allow the coffee grounds to steep for two to three days, creating a weak coffee solution.
Strain the liquid through a mesh sieve or a piece of cheesecloth to remove the grounds. Dispose of the coffee grounds.
Pour the liquid fertilizer around the base of the plant. Repeat once weekly.