Miracle-Gro Sulphate of Iron Ericaceous Soil Conditioner is ideal for ericaceous (acid loving, lime-hating) plants such as Rhododendrons, Azalea, Camellia, Heathers, Pieris, Hydrangeas, Roses, Blueberries and Acers. It helps make all soil nutrients available to plants allowing them to take up the nutrients they need. Works for several weeks.