whats the best plum tree to plant northcentral pa.zone 4-5.?

Answer 1

Most all plum trees should do fine where you are. I would buy it at your favorite L&G Center for two reasons. One, they will only sell plum trees that will flourish in your area (most will but they will make sure) and two, you will get a higher quality tree with a provenance for your zone.

Sometimes box stores get them shipped in from other areas and they don't do as well.