When discussing apple rootstocks and cultivars, understanding the terminology used to describe the tree is important. All apple trees purchased from nurseries are grafted or budded, meaning that there are at least two distinct parts of the tree. The scion is the above ground or vegetative portion of a grafted or budded tree comprised of the trunk, branches, leaves, and fruit. The scion is the cultivar or the part of the tree that has name recognition such as Gala or Honeycrisp.
|Photo by Jon Clements, University of Massachusetts|
The scion is grafted onto the rootstock which forms the root system of the tree. In apple trees, the rootstock will ultimately determine the height and spread of the mature tree. Suckers emerge from the base of the tree originating from the rootstock. If the scion cultivar dies, sometimes it is the rootstock that will continue to grow, usually producing fruit with different characteristics than the original cultivar and frequently of inferior quality. Often this is what can confuse homeowners as to what kind of apple tree was planted.
The architecture of the above ground portion of the tree also has specific terminology. The crown refers to the entire above ground portion of the tree with leaves and branches. The term “collar” refers to areas where intersections occur. The branch collar refers to the area where a branch attaches to the trunk or main shoot of the tree. The tree collar is at the base of the tree where the rootstock and scion join. A spur is a short woody shoot on an apple tree that primarily produces flowers and subsequent fruit. Spurs are shoots that usually grow very slowly, often less than ½-inch per year. Spurs typically terminate in a flower bud containing numerous flowers. Some trees are genetically dispossessed to produce most fruit on spurs, and are referred to as spur-type trees. Spur-type trees are generally smaller in stature than non-spur trees. Shoot length is shorter on spur-type trees resulting in a more compact tree so that trees can be planted closer together. Bourse shoots are vegetative short shoots that arise from beneath where a flower bud arises. Sometimes a tree produces very vigorous growth in a year resulting in excessive upright growth. These very long, upright branches are referred to as water sprouts and create shade within the tree and are unproductive. They should be removed during dormant (winter) pruning.
|Photos by Mike Parker, North Carolina State University|
Mike Parker, North Carolina State University
Emily Hoover, University of Minnesota