Are you saying they are not compatible or are you asking if they are compatible? You are throwing me off with your question mark at the end of your statement.

We grow large numbers of prunus besseyi here and they must be processed right away when they are ripe because they wont keep. The fruit rots within a couple of days of picking. We have a red variety that is sweet we grew from seed but the blacks are high in tannins and bitter. When they are processed into jelly they are delicious and you would never know the fruit was bitter. They are fast fruiting bush that is very drought tolerant. You can graft them over to another plum variety later which is what I do with them now. Japanese plums seem to be very compatible.

Rebeccalynne15 my black western sand cherries taste awful fresh and wonderful once they are processed into jelly. There are improved varieties some of which are delicious fresh. Here is my standard black variety(on the left) beside my unique red variety (on the right) that I grew from seed which is delicious fresh. Hansen cherries are a common improved variety of western sand cherry but their taste is similar to the wild ones. I'm told there was once a wide variety of western sand cherries grown that have since became lost to the years. This post was edited by ClarkinKS on Mon, Sep 15, 14 at 20:52

Late answer, I know.... I moved to a new rental last year. There are four 5'-6' bushes in the front yard. Imagine my surprise when plums started to develop on them! The kids cautioned me not to eat them, but I contacted the landlord who said people have been eating plums from that bush for 5 years and no one's croaked yet. Tart, but delicious fresh. Haven't tried to do anything more creative with them yet. He doesn't know the name, but I think they're carissa lanceolata, or at least that's what some research, comparisons to online photos, etc. have lead me to believe. Hope that helps!