F12 (or Ctrl+Shift+I) -> Console -> Switch context to game frame in combobox (default: top) -> Find "self.water" variable -> Set it to 1e999 to get +Inf -> Powerclick Water button for 10 seconds with 500 clicks-per-second -> ... -> PROFIT!!!
Don't worry, as far as I know, there's no legitimate way to grow tree this much without cheats. Well, not in the next few decades, at least. But still, it's kinda funny to see all your scripts going wild: tree grows this far with no affection on environment yet as soon as you build castle, shader becomes black-and-white. Yet, without any population, game events do not progress. And as soon as you get ~some~ workers, events go fast forward to bad end.
Also, winning battle 1 vs 287 with Powerclick is kinda lame, I almost feel sorry for all those poor souls who tried to beat it with their pure skills.