Rootstocks

Modern apple trees consist of two parts: the Scionwood and the Rootstock. Both parts are needed to replicate trees. The rootstocks offers many features including final height and grow rates, suckering, support needs, disease resistance, cold hardiness, and precocity (how early the tree can begin producing apples). 

There is no universal rootstock final growth height. We categorize our trees into Dwarf (0-12'), Semi-Dwarf (13-21'), and Standard (22'+). We also use a percent of standard when defining the final height of trees. This gives more of a range in proportion than an actual measured height. 

Suckering is the tendency for the rootstock to grow shoots and branches. These should be cut off in Winter to avoid transmitting disease while the tree is awake and growing. 

Most Dwarf trees will need some sort of post or trellis to grow. Because the tree stays small, the root system also stay small. A post or trellis helps keep the tree from leaning or tipping over.  Therefore, some dwarfing rootstocks require permanent or semi-permeant support. 

Like the scion wood, the rootstock can also carry disease resistance and susceptibility. This will vary from rootstock to rootstock. 

A note on cold-hardiness~ We have found no evidence that the rootstock can change the zone of a fruit tree. If a tree is only hardy to Zone 5, it will remain hardy to Zone 5, the rootstock does not make it hardy to Zone 4. Should evidence refuting this be published, we can amend this note. 

For further information detailing the rootstock and the primary source for these rootstocks, please see the U.S. Department of Agriculture National Institute of Food and Agriculture  Apple Extension website.