I found a stem or new little trunk growing up through a pen sized hole in a buried piece of scrap metal, as I was cultivating around a shrub. I've read that people who cut down residential trees almost always find metal in the trunk, because it had to grow around something of the sort. This one had two tiny stems, however and the metal was sharp around them. Not very thick though, since I could cut it apart with tin snips. If I hadn't noticed that though, do you think it could have grown larger through there, or around the metal starting from within it? Judging by the size of another new stem nearby, it was much larger around, as if the metal was preventing the other one from keeping up, but I'm not sure if they started growing at the same time.