Espoma Organic Holly-Tone for Evergreen and Azalea Plant Food, 4-3-4 Fertilizer, 8 lb., for acid-loving plants, such as hollies, azaleas, camellias, evergreens and hydrangeas. Also is excellent for dogwoods, blueberries, strawberries and rhododendrons. It is rich in natural organics and enhanced with bio-tone microbes. Used and recommended by professionals. Holly-Tone's all natural formula contains bio-tone, our proprietary blend of beneficial microbes. Bio-tone biologically enhances our natural plant food to ensure superior plant growth.