They say a pic is worth a thousand words...

Hybridizing different cherry species is a fairly complicated and rather obscure subject, but one that I have devolved some interest into.

-

Sweet Cherries (Prunus avium) have a 2n=16 chromosome number, though there do exist a few triploid and tetraploid varieties.

Sour Cherries (Prunus cerasus) have 2n=32

Wild Black Cherries (Prunus serrotina) have 2n=32

Capulin Cherries are considered by some to also be a member of Prunus serrotina, but are sweeter, and native to the warmer climate range of southern Mexico and Guatemala.

Cherry blossom trees are 2n=16, though many of the hybrid cultivars are sterile triploids (including much of the serrulata group) which have 3n=24 chromosomes. (sterile means they can only be propagated by cuttings)

Protocols for Micropropagation of Woody Trees and Fruits, edited by S.Mohan Jain, H. Häggman, p403

-

Generally if you crossbreed a sweet cherry with a sour cherry the offspring will produce fruit but the seeds will be sterile, because the two species have a different number of chromosomes. This is analogous to crossbreeding a horse and donkey together, which results in a sterile mule.

There is a hybrid cherry variety known as Mesabi that was the result of a cross between Bing (sweet cherry) and Montmorency (sour cherry).

-

Can an ornamental cherry be used to pollinate a fruiting cherry tree? I have found one published source that confirms this is possible:

"Since there is no low-chill germplasm available for sweet cherry, the only other alternative is to go to another species of cherry for this trait. Several species have been used in crosses with sweet cherry with occasional success with Prunus pleiocerasus and Prunus campanulata. In 1957, W.E. Lammerts made a cross between P. pleiocerasus and P. avium 'Black Tartarian'. This hybrid is very low-chilling (<200 CU ) but not self fruitful. The hybrid was repeatedly crossed with sweet cherry and P. campanulata. In the mid 1970s, the Florida program developed several seedlings by using mixed pollen (P. campanulata and 'Stella'). All the hybrids had pink blooms and thus were probably hybrids with P. campanulata. Several of these seedlings were fruitful. Although the size is still small, this germplasm is useful for the development of low-chill sweet cherries."

Temperate Fruit Crops in Warm Climates, edited by Amnon Erez, p216

For anyone thinking about actually doing this, I will point out here that Yoshino is a terrible pollinator, while Kanzan is a sterile triploid. These are by far the two most commonly encountered cherry blossom varieties.