KAPPA is our favourite chum(cherry x plum cross) along with Manor.  Both have purple black skin (when fully ripe) but Manor has red flesh while Kappa has green/yellow flesh. If you eat chums before totally ripe they will be sweet but astringent( like our native chokecherries. Some like to eat them at this stage and others make wine, jams, etc with the unripe fruit.  Best eaten when fruit is dead ripe( black)...when the delicious,sweet, fruity, plum/cherry flavour excels.. Both Manor and Kappa grow as a weeping bush of 6 ft high X 5 ft wide when mature. Precocious(quick to fruit) and very productive with the branches almost touching the ground with the incredible fruit load . Profuse, fragrant flowers adorn naked branches in spring...very pretty! Kappa is very cold hardy(zone 2) and likes dry, windy sites in full sun. Kappa needs another chum variety nearby for cross pollination.