sheltered from wind and sun, just half an hour, hour or so of early morning sun. The older branches I stuck in pots just like that. Some 6 or so herbacious branches enclosed in a plastic bag.
It sprouted once before. I think I pulled the sprouts off in May or June. It's time to cut back all my other mulberry stumps anyway so hopefully if I pull the sprouts off again it will go back to being a stick.