Nectarine trees start bearing fruit when they're around 3 or 4 years old. According to the Pennsylvania State Department of Horticulture, the main causes for fruit trees failing to produce fruit are overfertilization or overpruning. Both force trees to put all their energy into growing wood instead of flower buds. Fortunately, both situations can be corrected. Other causes of non-fruiting, such as frost, are harder to control.
Test your soil to determine if fertilizer or other amendments are needed. Nectarines prefer soil with a pH of 6.5. In addition to soil tests, check growth rate. Nectarine trees should show 18 inches of new growth every year. If your tree isn't showing this much growth, it needs to receive additional nitrogen when you fertilize the following spring. However, if your tree shows more than 18 inches of shoot growth, it means you're either overfertilizing or overpruning. Even if you don't fertilize your tree, it could be receiving too much fertilizer if you fertilize the lawn area around the tree. Don't apply extra fertilizer within 5 feet of the tree's drip line.
Nectarine trees should be pruned late in the winter to avoid injury and infection caused by bacterial canker organisms. When pruning, first remove any broken, diseased or low-hanging branches. Next, remove any large upright shoots that may be growing on the inside of the tree. Prune small shoots with a diameter less than that of a pencil. Leave branches that are 12 to 18 inches long. Cut back any vigorous upright limbs on the scaffold branches. Nectarine trees should be trained to have an open center that allows sunlight to reach all the branches and permits the movement of air. Keep the height of the tree around 8 or 9 feet.
Fruit can't form if temperatures drop much below 29 degrees Fahrenheit. Damage can occur any time after the flower buds begin to swell and may not even be noticeable because the flowers might open, but no fruit will set. Examine flowers a day after you suspect frost. Flowers with dark brown or black centers will probably not produce fruit. Nectarines are among the least winter hardy fruit trees. If you live in an area where the winter temperature regularly drops below minus 15 degrees Fahrenheit, your tree won't be able to consistently produce fruit.
Poor pollination is another reason why nectarine trees don't produce fruit. Nectarines are self-fruitful so you only need to plant one variety of tree in your yard, but you still need bees to carry the pollen between flowers. Pollination is reduced when insecticides kill bees or when cold weather, rain or wind reduce their movement.