Damson is a subspecies of the European plum (Prunus domestica subsp. Institia) that is native to Great Britain, and is actually believed to be the ancestor of European plums. It has been used for centuries for good reason.
Their fruits have a deep blue skin and they are more oval than round, and have a rich flavour that is both sweet and astringent. They are famous for being made into jam, even though they are clingstone.
Cold hardiness: Damsons are cold hardy, so much so that they have a history of being used for hedges and windbreaks.
Pollination: Damson plums are self-fertile, so you only need one to get fruit. Also, damsons produce true-to-type offspring, which is unusual with fruit trees – meaning that a seedling will turn out very similar to the parent.
Disease resistance: Moderately resistant to black knot, a very common disease of plums.
Rootstock: Marianna 2624.
Image 1: Jonathan Billinger.