[SunkenCiv]

Air-layering, and I’d imagine that, as with some of the US species that were nearly wiped out, there’s an active breeding project.

https://search.brave.com/search?q=American+Elm+Project

https://tacf.org/

https://search.brave.com/search?q=pawpaw+tree

[Fai Mao]

There is also a society for American Chestnut trees

[exnavy]

Reminds of Hartwick Pines State Park in Michigan. 29 acres of original old growth trees, the last of the North American old growth forest.

[Pete from Shawnee Mission]

SC As they push up suckers, put a clear plastic pot with a hole in the bottom over it. Put a black out cloth or plastic around the pot to shield any developing roots from sunlight. Add soil around the base of the sucker. Keep adding to encourage the sucker is growing until it above the top. Water regularly.

Wait a year or so for roots to develop in the pot. Take off the sun shield and see if the roots have grown. If yes, cut under the bottom of the pot and replant in another favorable location.

Works for figs, it will work for these.