Down To Earth’s Acid Mix 4-3-6 is a fertilizer blended for plants that thrive in a low pH soil like blueberries, raspberries, rhododendrons, azaleas, hydrangeas, evergreen trees and shrubs. To encourage lush flowers and fruit, apply DTE Acid Mix 4-3-6 in early spring for vegetative growth and again when blooms appear. Fall applications promote root growth and boost resistance to extreme winter temperatures.