Improve the color and general appearance of your hydrangeas with Bonide Soil Acidifier. This ready to use soil acidifier lowers the soil pH while improving hardiness, color, and general appearance of your acid loving plants such as blueberries, blue hydrangeas, azaleas, trees, and turf. To correct nutritional deficiencies to your soil or to reduce soil pH, apply to soil in the spring and fall. Bring out the beautiful blues in your acid loving plants with Bonide Soil Acidifier. Not for sale in California.