M. Frary
Bonsai Godzilla
First off. Where in Michigan are you? You're either near me or in the U.P.zone 4
I just started digging the Jacks up last year. Out of 8 4 are alive. All collected in spring. Going to try summer collecting this weekend. Fall is out for the reasons you stated. It's only 3 weeks long.
I've just been digging them up the regular way. Dig to the diameter of the bucket it's going in. They like their roots to not be messed with too much.
The sand is a problem. They like it. I'm thinking about trying ones on the edge of wet areas. They may have compact root systems.