There are several plum species native to North America such as Prunus americana, P. maritima, and P. nigra. These American plum species have adapted well to the climatic demands of our region, but their fruit quality may leave something to be desired for many. Japanese or Asian plums on the other hand have desirable fruit characteristics but lack the hardiness required to grow in our zone. Hybrid plum varieties seek to combine the best of both by crossing Japanese plums to hardy American varieties. Quite a number of hybrids have been release through the years including many from the University of Minnesota. To learn more visit the University of Minnesota Extension site on stone fruits for northern climates. There you can learn about what cultivars are available, the pollination requirements for the various cultivars, as well as other stone fruits including cherries, apricots and peaches.