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 Spyâ€™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?