About 12 to 15 years ago I grafted a Northern Spy to a semi dwarf Golden delicious, which was about 6 to 8 years old. After about 3 years I got 3 or 4 nice Spy’s that went full term. Since then I only get a half dozen or so blossoms that drop or only grow to the size of a golf ball and drop. The Golden Delicius part has a normal yield. Any suggestions? John

John:

Your tree is showing classic signs of multi-graft inbalance, where one variety dominates another. You should graft the Northern Spy onto it's own rootstock. You can speed up the fruiting on the Northern Spy by using a very dwarfing rootstock like Bud 9 and tie the brances down past horizontal in order to make the stubborn variety fruit earlier.