IIRC, ALJ mentions some of them reproduce through apomixis. (asexual reproduction via seeds) I suppose it would be hard to tell for years whether that happened, or whether it merely inbred itself. (or cross bred if you have compatible Rosaceae around)

Yes, what davidrt said. I see no particular harm in trying it though. Mountain ash, although a short-lived, disease-prone member of the rose family, has much to offer for wildlife and human aesthetic delight. For that matter, I've seen them many a time growing as volunteers up in the crotches of big, old maples, etc. Pretty tough survivors despite their short lives.

+oM