Peach trees have a productive lifespan of roughly 12 or more years, according to Michele Warmund at the University of Missouri, with mature trees producing an average of three bushels of fruit each year. With proper care, minimal cold damage and healthy growing conditions, peach trees can live significantly longer. Peach trees at roughly 4 to 5 years are considered to be mature and should be cared for as older trees.
Water your peach trees to keep the soil moist all year, increasing irrigation in the summer to suit the warm weather and peak fruit growth. Decrease deep irrigation in the late fall to slow growth and prevent freezing of water around the roots.
Prune your mature peach tree lightly to remove any dead, damaged, diseased or abrading limbs or branches. Prune out any large, upward facing shoots or water sprouts in the canopy or on the lower trunk. Remove lower hanging branches on the tree to lift the limbs off of the soil and create clearance, if needed or desired. Place all cuts down to the parent branch, just outside the swollen branch collar.
Feed your older peach tree twice each year in March and August. Apply a 10-10-10 or 12-12-12 fertilizer in March giving 1 cup of fertilizer for every year of the tree's age up to a maximum of 10 cups. Apply calcium nitrate in August giving 1 cup of calcium for every year of the tree's age up to four cups. Cast the fertilizer around the base of the tree away from the trunk and extending to just past the drip line. Water until the soil becomes drenched to a depth of 6 inches.
Thin young peach fruits roughly a month after bloom has finished. Removing excess fruit will preserve the tree's energy, improve the quality and size of fruit and prevent limbs from being overburdened and breaking. Pinch off the young fruit buds with your fingers leaving 6 inches between fruit.