What do you do with your used coffee grounds? If you put them in your compost bin, that’s not bad. But if you have a garden, save your coffee grounds for that. Used coffee grounds make good soil amendments, there’s a lot of phosphorus, potassium, magnesium and copper, and they also release nitrogen into the soil as they degrade. Acid-loving plants like hydrangeas, rhododendrons, azaleas, blueberries, carrots and radishes can get a boost from fresh grounds. However, keep them away from where you plant tomatoes, they’re not big fans. Used coffee grounds also improve the water holding capacity of the soil and decrease weed growth. You can sprinkle them around the top of some plants, but for things like vegetables, dig into the soil about 6 to 8 inches.