The lights are on
Oasis is a hidden area/quest that you can find somewhere at the western part of the north east wasteland near the top of the map in a maze-like area nearby radiation pits and a super mutant base. It has lots of trees. It takes a long time to find so don't give up so soon.
When you get there there will be 1 or 2 people called "treeminders" who live in Oasis. Once you enter this old guy will make you drink this strange crap and preform this stupid "so called" ritual and the screen will get green around the edges(alot like when that flood thing is talking in Halo 3).
You will then faint or something like that and awake in a new area with a tree in the middle. Talk to it. It will explain everything and tell you to kill it. Later the old guy will talk to you again andtell you to let the tree live. After that some old lady will talk to you she wants you to do something that makes trees grow faster. No matter what you have to go to the same place and the same stuff though. You go to a cave with a bunch of mirelurks. Everything else is pretty staight forward.
whoa. its way cooler to flame him. FREAKIEST. SCREAM. EVER.
To make this guide better you should tell exactly how to find oasis because it is a little hard to find. You should also tell them that to go through the cave there is a underwater passage to swim through in the underground pool because it is hidden. Last but not least you can just take a flamethrower to Harold the Tree Ghoul and kill him, but you have to fight the treeminders.
By the way, I featured more details and used more feeling in my blog post. (I did this before finding the guides)
I know that. But the thing is, That bob thing grew out of his head and now he is in the form of a tree (sort of).
The "tree's" name is Harold and he is a ghoul, not a tree. He is a recurring character throughout all 3 numbered Fallout games and Brotherhood of Steel.