How can coffee grounds be used as fertilizer?

Coffee grounds contain substantial nitrogen and potassium, both important for plant growth. They also includes many other trace minerals and carbohydrates. This also makes it a good fertilizer.

But since coffee grounds lack phosphorus (used in plant food for flowering plants) it is better for use on non-flowering shrubs, foliage plants and grass than flowers.

For "casual" use, let them dry first (otherwise they can develop mold and that's not helpful for plants) and then work them lightly into the soil.

If you compost, just dump them into your regular compost bin; they have a carbon-to-nitrogen ratio of 20:1, about the same as grass clippings. After used to make coffee, grounds contain up to 2% nitrogen. They are acidic with a pH of between 3.0 and 5.0, making them perfect for mulching rhododendrons, azalea and other acid loving plants.