Maybe there is language barrier here. It is not a conventional scientific experiment it is more of a common usage of the word. I am trying something I have never tried before and seeing what can be observed and learned from it.

What I learned is that Elms are easy to start from seed. American elms will regrow from the stump. Elms started from local seed are cold hardy in zone 3 even in pots buried in the ground. Although it's nice to have potting soil it is unnecessary for elms.