Dwarf vs Semi-Dwarf
Dwarfing rootstocks typically produce trees that are about 30% to 60% of the size of trees on seedling rootstocks, with a mature height of about 6 feet to 12 feet. Depending on the soil, scion cultivar, and training system, trees on dwarf rootstocks can be spaced at 20 feet x 14 feet (173 trees per acre ) to 14 feet x 4 feet (778 trees per acre). Some of the more progressive apple growers, in regions with less vigorous growing conditions, are planting very high tree densities with spacings of 14 feet x 2 feet with 1,556 trees per acre.
Semi-dwarfing rootstocks typically produce trees that are about 60% to 90% of standard size, with a height of about 14 feet to 22 feet, depending on the rootstock. Semi-dwarfing rootstocks were commonly planted at a spacing of 22 feet x 16 feet (132 trees per acre) during the 1960s through the 1980s.