There are two main ingredients in the root graft. The first is the root system. This is called the stock. In the case of Fat Alberts, the stock is the root system of a Colorado blue spruce. The Colorado Blue is used because of its excellent track record with hardiness and growth patterns. The second ingredient is a cutting from the tree that the grower wants to reproduce. This is called a cion. The cion would be a small cutting from a Fat Albert. Grafting connects the stock to the cion. It is necessary that the stock and cion be roughly the same size. An incision, in the form of a tongue is made in the stock and the cion. This allows the cion and stock to fit together securely. The connection is then bound with string and covered with wax.

Grafting can also be used to repair a tree. A cion can be attached to an established tree to form a new branch. Root grafting is just one form of grafting, there are numerous other methods that are also quite effective. Grafting is a century old technique that has consistently produced good results. To see the results of a graft, look at any of the small crabapples at Miller Nursery.

Reference: The Standard Cyclopedia of Horticulture, Volume 2