Starting an orchard
Apple orchards are established by planting two or three year old trees. These small trees are usually purchased from a nursery where they are produced by grafting or budding. First, a rootstock is produced either as a seedling or cloned using tissue culture or layering. This is allowed to grow for a year. Then, a small section of branch called a scion is obtained from a mature apple tree of the desired cultivar. The upper stem and branches of the rootstock are cut away and replaced with the scion. In time, the two sections grow together and produce a healthy tree.
Rootstocks affect the ultimate size of the tree. While many rootstocks are available to commercial grower, those sold to homeowners who want just a few trees are usually one of two cultivars: a standard seedling rootstock that gives a full-size tree, or a semi-dwarf rootstock that produces a somewhat smaller tree. Dwarf rootstocks are generally more susceptible to damage from wind and cold. Full dwarf trees are often supported of posts or trellises and planted in high density orchards which are much simpler to culture and greatly increase productivity per unit of land.
Some trees are produced with a dwarfing "interstem" between a standard rootstock and the tree, resulting in two grafts.
After the small tree is planted in the orchard, it must grow for 3-5 years (semi-dwarf) or 4-10 years (standard trees) before it will bear sizable amounts of fruit. Good training of limbs and careful nipping of buds growing in the wrong places, are extremely important during this time, to build a good scaffold that will later support a fruit load.
Apples are prone to biennial bearing. If the fruit is not thinned when the tree carries a large crop, it may produce very little bloom the following year. Good thinning helps even out the cycle, so that a reasonable crop can be grown every year.