prunus nigra, the elusive canada wild plum

prunus nigra, the elusive canada wild plum. distinctive double bumps on the leaf margins (the profile is called crenate, the sharp version is called serrate as in serrated), fruit over 1" and oblong shaped, ripens around now through early sept. I'm finding these in old orchards, rootstocks from decades ago, they used mixed seedlings from shelterbelts and nursery stock so the genetics are all mixed together, but sometimes you find a tree that strongly presents as americana or nigra. these in between ones, I'll have seeds for sale this winter but not sure exactly what to call them, hybrid wild plums maybe. but to find the real prunus nigra is a treat, considered the best pollinator plum with more of a tree form, less suckering than americana.