You may have noticed your local coffee shop offering free coffee grounds to gardeners. Although it's true that coffee grounds can act as a slow-releasing fertilizer for some plants, it can invite mold and other problems if not properly used. So, here's the break down of when and where to use coffee grounds in your garden.

Coffee grounds add acidic nutrients into the soil, so they are most beneficial for plants that yearn acidic earth, like roses and columbine. The great people at Crescent Bloom organized a list of acidic soil loving plants. Evergreens also pine for these roasted dregs in their root system.

Grounds are are also full of other nutrients like iron, and the caffeine can encourage plant roots to spread. However, grounds should only be applied fresh and in a thin layer once a year. If you apply them too thick, they are more likely to mold and that causes more problems.