Monkey Puzzle Tree

Let's talk about the Monkey Puzzle Tree. No, that's not how I start most conversations but now that I think about it, that would be a great way to get some room when I'm waiting in line at the grocery store. If I said it really intensely...
Anyway, the Monkey Puzzle Tree, or Araucaria araucana, for the smartie pants (pantses? panti?) in the room, is a spiky Chilean Pine native to Chile & Argentina. Because of their unique look they have been cultivated around the world and there are numerous trees of all sizes and shapes in the Vancouver area. The tree itself is not what's important here though. (No offense to you, tree)
What's interesting to me is the tradition that the tree has created. Much like the Volkswagon Beetle phenomenon the Monkey Tree lets you inflict pain on the first person you see after spotting the tree. It works like this: you and a friend are walking along a street. You spot a monkey tree before your friend does. You reach over and pinch them. Legally, they are not allowed to do anything back to you. Well, legal in the playground way.
There are some who believe you should say "Monkey tree, can't touch me!" when you perform the pinch but this isn't necessary, it's only a curtesy to those who may not know the game. Or it may be used as a quick explanation on someone with a short temper who might otherwise slug you. Also, the harshness of the pinch is up to the pincher. Some may like to do a light, playful one while others want to leave marks. It's pincher discretion.
Like the VW "Punchbuggy" there are some other rules. You can't perform another pinch with the same Monkey tree. You can, however, pinch another person with the same tree provided the person wasn't with you the first time you passed the tree. Also, you can only perform one pinch per person in a 24 hour period on a tree. The next day, it's fair game with that tree. But you don't want to be a jerk about it and constantly work the same tree. It's also bad form to map out the trees and make your route go by all of them. That's just mean.
There are probably some more rules but that's basically the gist of it.
I don't know where the tradition came from or even how I come to know it. When I did a search on the internet I only got a couple of mentions of it and those had no knowledge of the origin of the Monkey Tree Pinch. So if anybody knows why it's ok to pinch the crap out of someone just because you saw a tree, let me know.
Oh, and in case you'd like to be a part of this vicious game but don't know what a Monkey Tree looks like, I've included some images for you to study. But I'm not going to tell you where some are, you'll just have to be on your guard.