We have black walnuts trees out here, and there is not much difference to me between them and the ones you can readily buy in the store. However when you go to pick them, they do turn your hands an awful color.
My kids daycare had some of these trees, they tried hard to keep them picked up and the kids away from them. One day though, my oldest found a few that were missed and it took almost a week for the stains to vanish :lol: :lol: :lol: