Water peach trees during dry periods. If they are dealing with drought stress, there is not sufficient water to aid in cell growth and carbohydrate production.
Prune the trees in June. Develop an open-center shape that allows sunlight to penetrate the canopy. The more light, the bigger the peaches. Remove old branches, as well as those that rub or cross each other, using pruning shears or a pruning saw. Cut off vigorous upright shoots that form in the center of the tree after blooming. Make the cuts where they meet other wood.
Thin peaches to increase fruit size three to four weeks after bloom. Remove them by hand, targeting those that are smaller. Leave the largest peaches intact. Remaining peaches should be spaced every 8 inches.
Check the soil. Peach trees often are impacted by a lack of nitrogen and potassium. Collect a soil sample and have a university or cooperative extension lab test it for nutrients. Amend the soil based on the test results.