thanks for the thoughts, everyone. Still can't tell what my cabbage-looking volunteers are. I don't think I've had anything brassica-like in there except the brussels sprouts but my memory is challenged, lol.
duckduckgoose, if it were mine, I'd leave it! I suppose you could train either one up the trellis, right? (Not that I've ever done that - if I do this will be my first time!)