I love your title, and I wish my aged brain could recall from whre it comes.

Thank you for giving me the phrase "volunteer tree." I'd never before heard it; it makes the poor trees seem even more unfortunate, doesn't it? "I thought the lawn would look much nicer if it had a tree, so, well, I ... sort of dropped myself here. And grew. All on my own. Because I thought you'd like me." *awkward pause* "You don't. Well. I suppose you'll have to dig me up, then — no, no, I don't mind. My mistake. Don't bother your head about it. What? I am not crying. Trees don't cry!"

Seriously, though; good luck on taming the back yard. It's definitely the kind of thing that would have gotten away from me.