it is highly unlikely to use plum as root stock for apples. You can use plum as rootstock for other plants of genus 'prunus' like peach, apricot or even almond, but not for apple (malus).
the closer they are related, the better your chances for a successful graft.
I myself have gotten excellent results grafting apple scions onto the prodigy of store-bought apples. Just excise the seeds out of few apple cores and plant them in soil immediately before they dry out. I graft my scions the following winter and I've gotten 80-90% success that way. Grafting got so easy that I started grafting multiple varieties per tree. My personal best so far is 5 varieties on one seedling. In my own experence, apples only graft onto apples and pears only onto pears. I've read somewhere that either apples were grafted onto pear rootstock, or pears onto apple rootstock, but in my hands it didn't work.
For grafting Japanese plums, almond rootstock has worked well for me. This is what Luther Burbank used more than 100 years ago. Just go to Trader Joe's and pick up a bag of raw almonds and plant them in soil. After they've germinated I've successfully grafted plum, peach, necturine, and apricots onto almond stock.
Location: Anjou ,France
posted 6 years ago
Oh well worth an ask I thought . I shall see about the apricots though.
Living in Anjou , France,
For the many not for the few
well - that depends. In this case it depends on the root stock choosen, for the 'original' tree. Suckers are shoots emerging directly from the rootstock of the plum, so they might express very different fruit qualities than the plum you know. Rootstock varieties are usually selected for their hardiness, growing size, disease resistance etc. not so much for their fruit quality. If you don't know, which variety was choosen for the original tree, it is impossible to tell. It is very likely, that you get some fruit, it is unlikely, that it the same or even similar to the 'original'.
But if you have the place to try, go ahead. There are some plum varieties which are raised from seed, so you might be lucky.
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