Holly-tone fertilizer is for acid-loving plants, such as hollies, azaleas, camellias, evergreens, hydrangeas, dogwoods, blueberries, strawberries and rhododendrons. It is rich in natural organics and used and recommended by Professionals for decades. Holly-tone also contains Bio-tone®, Espoma’s proprietary blend of beneficial microbes. Bio-tone biologically enhances Espoma’s plant fertilizer to ensure superior plant growth.