Thanks for the A2A.

“Young, vigorous fruit trees up to 5 years old are best for topworking. Older apple and pear trees of almost any age can be topworked but the operation is more severe and those over 10 years old must be worked at a higher point. Hibernal, Columbia, or Virginia crab, because of their 3 vigor and their strong, well-placed branches, are very good understocks.

Young trees should have 1 to 2 feet of branch between the trunk and the graft. Otherwise the good crotch formation of the understock will be lost by the trunk expanding past the union.

Trees up to 5 years old can be grafted at one time. On older trees about half – the upper and center part only – should be worked at one time. The remainder should be worked a year later.”

Source: Grafting and budding fruit trees

Some trees that can be grafter onto others, and vice-versa:

• Apple, pear, hawthorn, quince, mountain ash
• Plum, cherry, peach, nectarine, apricot
• American Persimmon, oriental persimmon, date-plum
• Pecan and the hickories
• Beech, oaks, chestnut