Espoma Holly-tone 4-3-4 Plant Food is for acid-loving plants, such as hollies, azaleas, camellias, evergreens, hydrangeas, 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®, a proprietary blend of beneficial microbes. Bio-tone biologically enhances natural plant food to ensure superior plant growth. Mix organic, granular fertilizer with soil to encourage healthy growth of acid loving plants. Slow-release fertilizer for extended feeding.