might try this in the fruits and orchards forum, butI will say this, I dont think you can graft apples to plums.

Mike

Forget about it. Plums do not live that long compared to apples. They also grow at a different rate than apples and their wood is not as strong as apple wood.
George

Just noticed a tree today on the property that I live on that was grafted some time in the way back. It looks to be a plum/apple tree, though I can't be sure just from the flowers. One branch (which has white blossoms) which I believe to be apple seems to be the original stock and the rest of the branches seem to be plum (which have very different looking pink blossoms).

I have heard that you can't graft apples to plums or plums to apples, so I'm not sure how this tree came about. I will take a picture of it tomorrow and post it so that maybe someone with better knowledge can tell me if it really is an apple/plum graft or if I'm mistaken.