Orchardists categorize apple trees by their growth habits and fruit production. Dwarf, semi-dwarf and standard are the three main categories relating to the mature size of apple trees. Many gardeners and small orchardists prefer to grow semi-dwarf apple trees because of their manageable height in the landscape and their ability to produce quality fruit. Semi-dwarf varieties grow to about 10 to 15 feet in height. Like many types of fruit trees, semi-dwarf apple trees require regular pruning to encourage the production of abundant fruit.
Prune broken or dead branches with a pair of sharp pruning shears. Make the cuts slightly above the damaged growth to include a small section of healthy limb.
Disinfect the pruning shears between each cut with a diluted solution of bleach and water, mixing about 9 parts water to 1 part household bleach. Dip the shears into the water to guard against the spread of disease.
Train young semi-dwarf trees as soon as they are planted. Select the strongest, central branch to use as the main trunk on each of your trees. Cut away all other vertical branches near the central leader, leaving only the side branches that extend outward from the central leader. Make these initial pruning cuts at the base of the branches, near the intersection of the branches and the trunk.
Cut out any side branches that grow directly opposite another side branch, encouraging branches to alternate along the sides of the trunk. Prune out any branches with narrow crotches; these side branches grow outward from the trunk in tight angles of less than 45 degrees. Cut these side branches to encourage the semi-dwarf apple tree to form an open, outward pattern of growth.
Prune the central leaders on the apple trees the next spring. Cut this central leader to a height about two-thirds of its original size. Make this pruning cut slightly above a side branch. Remove only damaged growth and branches that cause crowding until the semi-dwarf trees begin to mature and produce fruit.
Prune mature trees in the early summer to remove suckers near the roots and side branches that crowd the other branches, limiting airflow and sunlight. Cut out heavily fruiting clusters during the summer when the fruit begins to appear on the branches.
Pinch out excess fruit to allow only one cluster of fruit every 6 inches. Prune each remaining cluster to allow only the healthiest fruit to remain in each cluster.