Blueberries Alive! 100% All-Natural Fertilizer (5 lbs) Boosts plant health and blueberry yields. Maintains acidic soil pH blueberry plants require to thrive. Blueberries need a pH of specifically 4.5-5.5. Enhanced with minerals and natural trace elements. Apply at 5 lbs. per 100 sq. ft. in early spring and again when fruit starts to form.