Blueberries are sensitive to the nutrients in the ground, and it is possible to overfertilize them. Applying fertilizer twice per year provides all the nutrients these plants need to produce an abundant crop. They do well with a product developed for use with rhododendrons or azaleas.
Owners should apply fertilizer just as the leaves start to show after the dormant period. The second application is 8 to 12 weeks later, just after pruning the plants. The U.S. Highbush Blueberry Council recommends applying 1 tablespoon of 10-20-10 fertilizer once the plants are established and increasing by 1 tablespoon for each year after planting until each plant receives 8 tablespoons total.
Blueberries prefer an acidic soil, with a pH of 5.0 for maximum production. However, it is important that gardeners lower the pH slowly to avoid damaging the plants. Apply small amounts of conifer sawdust, ammonium sulfate or sulfur. If leaves begin to yellow after applying sawdust, the plant is deficient in nitrogen.
While fertilizing provides the food the plant requires for producing fruit, pruning ensures maximum fruit production. Prune after the plant forms blooms, removing low growth and discolored branches. Maximum fruit production is achieved by removing one-third to one-half of the existing branches.