With their smaller size than regular apple trees (Malus domestica), semi-dwarf trees are easier to prune and require less growing space. Unlike dwarf apple trees, they do not require as much external staking for support and generally live longer. Depending on what your needs are, you may require up to two semi-dwarf apple trees to provide enough fruit. Apple trees grow best in U.S. Department of Agriculture plant hardiness zones 3 through 8.
“Northern Spy” is a variety of semi-dwarf apple tree that grows quickly and requires regular and significant pruning in order to thrive. In turn, the “Honeycrisp” variety is slower growing and requires less pruning. For quick growing varieties, space the trees between 14 and 16 feet. For slower growing varieties, leave 10 to 12 feet between trees.
Pruning and Spacing
How often you prune your semi-dwarf apple trees will affect how closely spaced together they can be. Spacing your trees between 12 and 18 feet will let you prune your trees once a year. If you prune less regularly than this, space your trees farther apart. For trees that are pruned several times a year, you can have as little as 8 to 10 feet between trees.
Ideal growing conditions for semi-dwarf apple trees are nutrient-rich soils that are well training and that have a steady level of moisture. Plant your semi-dwarf trees in an area that receives full sun. Mulch the base of the trees, leaving 6 inches of space from the trunk, to maintain a steady level of moisture in the soil. Prepare the soil in advance if it is poorly draining, and plant two types of semi-dwarf apple trees that blossom at the same time in order to ensure a harvest. Semi-dwarf apple trees do not self-pollinate, so you need at least one other tree that blossoms at the same time for a harvest.
Root Stock Type
As true-to-type fruit trees are propagated by grafting onto rooted cuttings, also known as root stock, the type of root stock will affect how far apart you need to space your trees. The M.7 and Geneva rootstocks produce semi-dwarf apple trees that can be grown 12 to 14 feet apart. MM.106 and MM.111 produce semi-dwarf apple trees that require more space to grow vigorously; often 18 feet or more between trees is required.