One of the easiest and simplest ways to see if two varieties could pollinate each other is to check their pollination or flowering groups. The flowering groups are not the only factor in determining compatibility between varieties, but they are a good starting point.

These groups are somewhat arbitrary (there is not official definition) but the concept is simple - each group contains varieties that flower at around the same time. Groups may be given letters or numbers, but they typically run from the earliest-flowering to the latest-flowering varieties in each species. This works for apples, pears, and most plums. Pollination is most likely to be successful with two varieties that are in the same group.

In cool temperate climates where spring lasts many weeks, such as the UK and northern Europe, you can assume that varieties in neighbouring flowering groups will also be compatible because the flowering will overlap. In continental climates where the transition from winter to summer happens very quickly, such as much of the USA and southern Europe, you can assume that varieties even two groups apart will probably still overlap and therefore have the potential to cross-pollinate.

In general, if your fruit tree is in flowering group 3, you could choose any other from flowering groups 2, 3 or 4 to pollinate it, and both would produce fruit. However, cherries tend to be much more particular than other fruit trees. Certain cherry trees could have their blossoms open at the exact same time and not cross pollinate to produce cherries. That means it may be more optimal to choose two cherries in the same group.

As you may have already guessed, the Flowering Group and the Cherry Group classification use two different systems.

While talking about grouping, we can also divide all cherry trees into two groups: those with 16 chromosomes, and those with 32 chromosomes. Sweet cherries and cherry blossom trees generally fall into the first group, while sour cherries and American wild cherries (including Black cherries and Capulin) fall into the second group.

Despite the different number of chromosomes, it is possible to crossbreed a sweet cherry and a sour cherry into a hybrid variety (such as Mesabi), but these hybrids generally produce sterile seed, and can only be propagated by cuttings. Some ornamental cherry blossom cultivars (such as kwanzan) are also sterile triploids, with 24 chromosomes.

And for anyone here wondering if they could use their ornamental cherry tree as a pollinator, Yoshino and the other related ornamental cherries in the prunus yedoensis group, are absolutely terrible pollinators. The only other ornamental cherry group that is popular in America (mostly in Texas and Southern California) are the Formosan cherries, and those have blossom times far earlier than most fruiting cherries.