If you have apple, peach, plum or cherry trees that bear fruit, they usually need to be fertilized every year. One of the best times is late fall. The fertilizer will be taken up by the roots to prepare the tree for vigorous new growth as soon as spring arrives. An abundance of nitrogen in the tree early in the season encourages development of a large leaf surface and promotes production of fruit. Usually the overall result is a better yield of higher-quality fruit in addition to improved vigor and health of the tree.
Go easy on fertilizing pear trees, especially with nitrogen, because it could make the more susceptible to fire blight. It is the succulent new growth on pear trees that is most likely to become infected.
A good safe rule for dwarf apple trees is 5 to 10 pounds of 10-10-10 fertliizer per tree. Dwarf peach, cherry and plum tree can take 4 to 8 pounds of 10-10-10 per tree.
Spread the fertilizer evenly on the soil surface from near the edge of the trunk to slightly beyond the spread of the branches. If grass is growing around the tree, be sure it is dry before applying the fertilizer. Otherwise the nitrogen may seriously burn the grass. If there is a mulch, work the fertilizer into it. If there is neither grass or mulch, work the fertilizer gently into the soil. Deep cultivation may cause root injury to the trees. After applying the fertilizer, water thoroughly so the nitrogen seeps down into the root zone.
If the fruit trees are large, give the apple trees about 15 pounds of 10-10-10 each and the others about 10 pounds each.
Do not fertilze fruit trees that have not yet started to bear fruit unless the soil is rather poor and they are not making satisfactory growth. The nitrogen could delay their starting to bear.
It used to be believed that fertilization of fruit trees in the fall could result in winter injury. On the contrary, research at Michigan State University has shown that the nitrogen increases tolerance to freezing weather: Peach trees low in nitrogen were killed outright in their cold climate. But fertilization in late summer can cause considerable damage.
Research at Ohio State University has shown that nitrogen applied annually is essential to good consecutive yields, particularly of apples, and may be of considerable help in over coming the alternate-bearing habit.
Research at the University of Maine has shown that fruit from trees adequate fertilized with nitrogen was definitely better flavored than that from low-nitrogen trees.