I keep playing around with the idea of trying sweet cherry trees even though they seem problematic from what I’ve read disease wise and borderline hardy for my zone. Anyways i was just on Fedcos website looking at the options and see Leningrad sweet cherry listed at zone 4. Is anyone growing this cultivar? I’m surprised to see it as i scoured the internet when starting to plant fruit trees years ago mostly interested in cherries at the time and concluded that romance bush cherries would be the best to plant(even though sour). After my first sample of romeo i have a renewed interest in something different as they were more sour than I expected. I only have mesabi (sour) to compare and i find it more enjoyable out of hand. Still crossing my fingers on juliet being better but have read on here that its not that much better.
In Russia, there are four varieties of Leningrad sweet cherry: Leningrad Yellow, Leningrad Pink, Leningrad Red, and Leningrad Black. Fedco sells Leningrad Black (it’s the most popular one of the four). It’s self-sterile, so you will need another sweet cherry for cross-pollination.
Sweet and tart cherries have very different flavor profiles. In my opinion, one is not a substitute for the other. I like them both, but it’s like apples and pears — each one has its unique flavor.
I have a 2 year old Leningrad black from Fedco in zone 4. It’s a beautiful tree and this year it blossomed. However I’m having difficulty finding a companion sweet cherry to pollinate it. I planted a Lapin from Fedco that is alive (not thriving). It blossomed right as the Leningrad was almost dropping its flowers–too late I believe. If anyone has a source for a good pollinating sweet cherry for zone 4, please let me know. I’d like to get another tree in the Leningrad series. Or graft another type to the existing black Leningrad.
I live in Leningrad (now it is St. Petersburg) Leningrad black cherry is not the sweetest, it will have a slightly bitter taste, add another variety to your tree and it will endure the winter more easily. and will pollinate.
Just from what ive read, I lean toward the newer disease resistant self fertile sweets like Black Gold and Stardust.
Is your Mesabi productive? Some say it is not very?
I believe it is a hybrid like Jubileum or Danube, and Kansas Sweet. Hybrids might be a tad more hardy from the tart cherry side. I lean that direction 
I believe Cupid is the sweetest and latest bloom of the Romance series.
@PaulinKansas6b My mesabi were decently productive I would say. Good enough for my needs. I had them in the ground for about 4 years before moving and was getting maybe 1 gallon off both trees. Basically it was enough for me to snack on them about every day for a month while outside. Those trees would be 7 or 8 years old now so I would have to drive by my old place sometime next summer and see if they are loaded or not.I have one planted at my new place but it froze back the 1st year. I’m suspicious that it’s a type of sweet cherry that was mislabeled. I went to the same store this year to get another and it had 2 tags on it one some type of sweet the other mesabi.
I would look at this chart it shows relative bloom times (and overlap between cultivars) for sweet cherries and which trees are pollen compatible. Zone 4 is pretty tough for sweet cherries and people usually plant hardier sweet cherries that bloom late to avoid late frosts in zone 4.
Most sweet cherries are not going to be hardy in zone 4. Cummins nursery lists Black Gold and White Gold as hardy to zone 4. With Black Gold they actually list the orchard site and the minimum temperature that the trees survived.
Gold is an older cherry with cold hardiness and is one of the parents of Black Gold and is just as hardy if not more so. All of the “Gold” cherries bloom late. I think you will have a hard time finding the combination of early bloom and being hardy at zone 4 as most sweet cherries are only hardy to zone 5. Maybe another Leningrad series would work but I have no experience with that series.