Can you help me identify my tree?

Species name: Rosaceae

Common name: you tell me!

Location: my backyard

Shockingly, I have managed to find a tree I can't identify. That might sound like a cocky statement, but that's certainly not how I intend it; if you have the right resources and identification keys you should be able to identify any tree growing in a planted area in a garden (any garden), but I am completely stumped! I've managed to narrow it down to the family based on the flowers: white flowers with five petals and numerous stamens. It should be reminiscent of strawberry flowers (since strawberries are also in the Rosaceae, or the rose family). That is where my abilities at identifying this tree end.

It doesn't matter what species I look at, native or non-native, none of them quite fit. The leaves are similar to serviceberry leaves, but the flowers are different (serviceberry flowers also have five petals, can be white but also slightly yellowish, but the petals are MUCH narrower than in these flowers). It looks similar to a Saskatoon-berry, but the leaves are much too pointy, not broadly rounded at the ends. The flowers look similar to crab apple flowers but the leaves don't have the prominent lobes of the wild crab apple or pacific crab apple, and don't have the correct leaf shape for the common apple or the siberian crab apple. Cherry leaves, also trees in the Rosaceae, are the widest at a point above the mid-line of the leaf (so if you were to cut a leaf in half cross-wise, the top half of the leaf would have the widest point, not the bottom half like would be the case with these leaves). It could be a pin cherry, but I've never seen the bright red berries that are characteristic of this species. Choke cherries are similar species, but the flowers are arranged in dense elongated clusters at the tips of the branches, which is not the case with the tree in my back yard. Canada plum is another possibility, but this species has characteristic thorn-tipped dwarf shoots which my tree doesn't have. This characteristic (or lack thereof) also eliminates all hawthorns, but they also have very different leaves with defined larger teeth, as well as the smaller serrate teeth (sometimes called "double dentate").

So what DOES this plant have? Well, aside from what you can see in the images (surprisingly enough, that leaf picture actually tells an interesting story, although I don't know if it means anything biologically). The leaves are always arranged in threes on the tips of short-shoots off of branches, even at the top of the tree. This tree is growing in a heavily-shaded area, and only the top of the tree would ever receive direct sunlight. Also interestingly, hardly any of the flowers develop into fruit, yet there are always tons of insects around the flowers scavenging for nectar and pollen while they are open (the flowers have no noticeable scent that I could discern). I went back to this tree (pictures originally taken May 26th of this year), and there's only one tiny fruit on one branch that I could see; it was about the size of a pea and completely green. I'll go back and update this blog if it grows and turns colour before it disappears in the hands of a bird or squirrel.

Here's your challenge for the day: help me identify it! Have you ever seen a tree like this before? Do you have one in your backyard? Do you work at a greenhouse and sell this tree? I'm almost positive it's a non-native species (only because of its lack of fruit production, implying it might have some sort of specialized pollinator that we don't have in Canada) but I might be off the mark. Someone tell me this is an incredibly rare species! :) Any and all help welcome.