You don't need 4 in 1 sweet cherries these days. You can grow Stella, Lapins, and a few other self pollinating varieties that should be hardy enough for your area. The biggest problem, as with anywhere in the east, is fruit that cracks from rain. A near ripe cherry will split with even a light rain. You can get a 4 in 1 if that is what you want, but you don't need it if all you want are sweet cherries.

I have read that in this instance that people can do two grafts. The native variety being the most hardy and strongest rooting, then a short intermediary piece which can bridge between the native and fruiting varieties. Can anyone assist? Or know someone who can? I have cut down a large native cherry and would like to graft lapins and stella to the sprouts which are sure to come up this spring. "example taken from plum/almond stone fruit grafting" - " Also (and this is where the fun starts) most fruit trees in the Prunus genus are sometimes compatible with each other: almonds, apricots, nectarines, peaches, and plums all are compatible for grafting, but occasionally it's complicated. For example, some plum rootstock is not compatible with peaches or nectarines; and some almonds require an intermediate step before grafting onto some plum rootstocks."

I'd recommend you steer away from apricot if you have limited space. I took a course on fruit growing here in Edmonton and the instructor said the trees are fully hardy but the fruit buds are killed at -30C (can take as low as -34 for brief duration), and that you are lucky to get fruit once every 5 years here. Apple trees are so common (and you say there is one near you) that I think you could put in one apple and not worry about cross-pollination because the neighbour's trees will suffice. If you are worried about it, you could buy one of those apple trees that have two or more varieties grafted onto one tree (or do it yourself). I have a Pembina plum that wasn't producing much fruit so I grafted on two branches of "Perfection" plum (which has the same bloom period) and ever since then I get around 200 plums each year. I did the same with a "Ure" pear... grafted on two branches of some very sour pear but that allowed the Ure pear to get pollinated. (I don't recommend pear though, as most of mine just fall in the yard and attract a million wasps). Thgat's kind of rambling, but I hope it helps.

"subgenus" may be more appropriate (or maybe not, taxonomists have put both sweet and sour cherries into the subgenus Cerasus). All these different cherry species are very closely related, if one wants to consider them different species. This is one example where the line separating different species is not a clear one. It could even be possible to consider the different cherry families as subspecies. After all, if they can freely interbreed and hybridize with each other, can they not be considered members within the same species? (by this definition we could divide all cherries into only 2 groups: those with 16 chromosomes and those with 32) Or one could attempt to divide cherries into different families: Sweet cherries (P. avium), sour cherries, Black cherries plus Capulin native to the American continent (put into same group), and Asian flowering cherries. Perhaps better classification could be provided if taxonomists utilized multiple degrees of species relatedness/separation, because it is ambiguous whether some of the different cherries should be classified as entirely separate species or subspecies within a singular species, neither of which would be wholly accurate.