You're right, ..most have tart skin. I'm thinking the Supreme Plum, Pembina, Patterson's Pride, etc. ..but why do you need tart skin?

Here is a link that might be useful: Lets talk about Plum

That's what the wife loves. That or just a tart plum I suppose. But she was describing a plum tree her grandfather had when she grew up in California. Santa Rosa sounded close.

I have an Italian plum and the flesh is yellow and sweet but the skin is tart, that is why it makes an excellent tart. The 'wild' taste is in the skin. Mrs. G

Good to hear since I know I can grow them.

Superior is a very good tart plum. It was bred as a hardy plum, I don't recall the zone but its either 4 or 5.

Scott

This wouldn't be an issue if your wife wasn't so sweet already.....

The american plums tend to have quite a tart skin. When fully ripe, the pulp/juice is very sweet and aromatic, but the skin remains quite tart. You might look at getting a native plum or a variety bred from the american plums.

a good suggestion might be the wild goose plum, a sweet tart native plum, available from oikos tree crops.
native plum need less care

Wild goose plum sounds invasive and scary (thorns).

nobueno,

I have had no trouble with hardiness of Japanese plums here in Denver. The issue is not hardiness but bloom time; we usually get frosts that kill the blooms. I have Elephant Heart and Satsuma and my neighbor has Santa Rosa. We have had good crops the last few years.

The European plums, especially my Shropshire Damson, bloom later and therefore avoid the frosts.

I would have to say that it sounds like you are wanting a Santa Rosa. You will need a pollinator for it though. A Japanese hybrid would work well. But you should be prepared in case of frost at bloom time.

Try persian plums ( green or red). They are very tart before fully ripe without the bitterness of other premature plums.

Various Native plums can be quite tart, and also quite hardy....

I think in Zone 5 - I would either go with something Native, or with an European plum of some sort or another.... unless someone specifically has Japanese plum recommendations from way up north... I would worry that J. Plums would winter kill in harsh winters...

Thanks