Well the truth is...........
I dont have the slightest clue.
I found it growing between my Hibiscus Syriacus bush while doing some heavy garden pruning. It kinda blended in with the stems so I hadn't noticed it before. I thought "hey, that doesn't go there" and lobbed most of it off. That was about 3 weeks ago. Today I returned to my Hibiscus to airlayer the massive main trunk that will make a nice bonsai if I find a way to improve wound healing (that's where the pins come in actually).
Well turns out little guy had really strong and thick roots and actually had a really thick main trunk/root kinda thing, thicker than the actual trunk, growing well under the massive Hibiscus bush.
It was a massive pain to dig it out and since I had no intention to keep it I was anything but gentle and the stump took some hefty abuse. It's nothing but a miracle the bud wasn't torn off in the proces, and it might still die I guess.
I think it somehow originates from the roots of a massive tree that grew in that spot before it was felled by a storm 20 years ago, because I doubt any seed left there by a bird would grow such a thick underground trunk.
That tree was a Poplar according to my mother but I dont really trust her memory.
It actually had nice roots radiating outwards in all directions wich would form an excellent future nebari but I think I wasn't gentle enough and most of the roots probably wont make it either. But I decided to pot it anyway mainly because I got curious what species of tree we have here. And it would be a nice first victim to practice my "bark flap" technique on.
The cut I made 3 weeks ago was kinda ugly and torn so I made 4 incisions, peeled down the bark a bit (like a banana basically), cut another piece of the trunk and folded the excess bark over the wound. The bark flaps are kept in place with the pins. It's a technique I'm hoping to use on the Hibiscus im airlayering atm. When I lobbed of bigger branches in the past they never really healed / closed at all, so to make a convincing bonsai out of it I need to find a solution to this problem.