There are basically three main categories of apple rootstocks: standard (full sized), semi-dwarf, and dwarf. The rootstock you choose will determine the size of the tree, NOT the size of the fruit. So, even dwarf apple trees will produce full-size fruit. Your task is to choose one of these three types of rootstocks for your orchard. Information about each category of rootstock is given below:
Standard: Apple trees planted on standard rootstocks will produce large, full-sized trees that may grow more than 25 feet tall. They are very hardy and can be planted in a wide range of soils and climates. They are sturdy, long-lived (50 years or even longer), and productive (producing about eight bushels of apples a year when fully grown). However, because of their large size, they should be planted at least 30 feet apart. Therefore, if you choose standard rootstocks, you will be able to plant fewer trees in your orchard. Also, their large size makes pruning, spraying, and picking more difficult. You will eventually need a ladder (or a long-handled fruit picker) to pick your apples! Full-size trees also take longer to bear fruit. It will probably take five or six years (or maybe even longer) before the trees start to have a good crop. In spite of these disadvantages, if you live in a very cold area (USDA Zone 3 or colder), standard rootstocks are your best choice because trees grown on dwarf or semi-dwarf rootstocks may not do well in your climate. Space full-sized trees at least 30 feet apart. Rows must also be no closer than 30 feet apart.
Semi-Dwarf: Trees planted using semi-dwarf rootstocks will reach a height of 15 to 20 feet. They should be planted at least 20 feet apart. They may not be as hardy as full-sized trees but can be planted in USDA Zones 4 or warmer locations. They will produce about five bushels of full-size apples per year. They are not as long-lived as full-sized trees and have a life expectancy of about 20 – 25 years. They do not require staking. Because they are smaller than full-sized trees, picking and care will be easier. However, a ladder may eventually still be needed. Space semi-dwarf trees at least 20 feet apart and rows no closer than 25 feet apart.
Dwarf: Apple trees planted on dwarf rootstocks will grow 10 or 12 feet tall. They should be planted no closer than 12 feet apart. They will be less hardy than full-sized or semi-dwarf trees. Do not plant them in USDA Zones 3 or 4. Because their roots tend to be rather shallow and not very strong, dwarf trees will need to be tied to a sturdy stake. Dwarf trees will live for about 15 to 20 years and will begin bearing fruit in two or three years. They will produce one or two bushels of full-size fruit a year, and because of their smaller size, most of the fruit can be picked without a ladder. Place dwarf trees at least 15 feet apart and rows no closer than 20 feet apart.
Assignment extension for advance d students: There are many varieties of apple rootstocks. They have names and different characteristics, just like named varieties of apples. For instance, Antonovka is a commonly used rootstock for full-sized trees. It originated in Russia and is very hardy. Many rootstocks are available for growing dwarf or semi-dwarf trees. Quite a few of these were developed in East Malling, England. Therefore, you will see them listed as M. (for Malling) and a number (M 9 or M 27, for instance). So, to make this assignment a little more challenging, use the links below to read about advantages and disadvantages of rootstocks and then choose a specific, named rootstock for your orchard.