Our mature American Chestnut tree is well established enough that it dies back some every few decades and recovers. This year I got 50 or so chestnuts out of it. I ate a few, they are great and never seem to get the weevil that the Chinese trees we have do (basically if I don't process the Chinese ones immediately after harvesting in a hot water bath, they will have a grub bore out of them in a week or so).
Been trying to find people outside blight region (somewhere like Michigan/Wisconsin) to plant the American ones so they have a shot. This tree is not a result of any of the ACF's crossbreeding, it's just a survivor that's over 100 years old.