Coffee grounds provide plants with many of essential nutrients including magnesium, calcium and nitrogen. Theses nutrients are very beneficial to plants and are often found in fertilizers. The grounds can add a significant amount of acidity to the soil. Blueberries, roses, and gardenias are a few plants known to love acidic soil. Using coffee grounds for other plants may prove to be harmful. Before adding the grounds to any plant research it and learn if acidic soil is preferred.