护树人回避科技而偏爱自然，将所有人类苦难归咎于科技进步。对邪教的控制权由树父和叶母（桦树和月桂树）行使，对其事务拥有平等的发言权。 随着绿洲的壮大，大自然再次出现在废土上，邪教直面废土的敌意。尽管他们鄙视科技，但护树人继续使用枪支，以与敌人保持平等。 只有少数外来者被允许活到足够长的时间才能进入绿洲，尽管这种情况很少见。大多数人被拒之门外，有些人在试图强行进入时被杀，其他人则像掠奪者一样一见到就被击毙。
- Maple's garb reward for completing the Oasis quest in the favor of Birch.
- Poplar's hood and Linden's Outcast power armor both rewards for completing the Oasis quest in the favor of Laurel.
- The Lone Wanderer: "Any information you could give me on the caves below Oasis would be helpful."
Linden: "Oasis is located near what used to be an old mining town before the bombs fell. When the attacks started about 200 years ago, many people took shelter in the natural caves that dotted the area. The old gate that stands at the mouth of Oasis Cave is the last piece of architecture from those days."
- The Lone Wanderer: "How is it you're causing all of these things to grow around you?"
The Lone Wanderer: "What's causing this place to grow?"
Poplar: "In what we call the Harvest Month, the Great One creates seeds among his branches within seed pods. At the end of this time, the pods open and the seeds are carried quite easily upon the wind. It's quite beautiful. Wherever the seeds take purchase, they grow into trees, plants, grass or all manner of wonderful things."
- The Lone Wanderer: "Why do you call yourselves Treeminders?"
Birch: "We care for this place and keep it safe from those who would seek to exploit it. He gives to us, so we give back to Him. It's an arrangement that's worked well for almost two decades. We shun technology and embrace nature. That's the life of a Treeminder"
- The Lone Wanderer: "How did the Treeminders begin?"
Birch: "When I first beheld the glory of the Great One, I knew there'd be others who would seek to do Him harm. I also knew He would be calling others that he felt were pure of heart to protect Him. Right then and there I created the Treeminders... the Great One's last line of defense."
- The Lone Wanderer: "I think you're all a bunch of lunatics."
Birch: "Ha ha ha. I don't expect you to understand everything you see here. After all, you carry the taint of technology upon you. Treeminders shun technology and embrace nature. All technology has brought the world is violence and death."
- The Lone Wanderer: "Were you aware that Laurel gave me this Liniment?"
Birch: "Of course I am. I know everything that goes on in Oasis. Laurel is free to pursue whatever path she chooses. A long time ago, it was agreed that the Tree Father and the Leaf Mother hold equal say. I don't seek to change those customs. I just hope that when the time comes, you'll make the right choice."
- The Lone Wanderer: "If you hate technology, why carry weapons?"
Birch: "Sadly, the Wasteland is a hostile place and sometimes we're forced to defend ourselves against it. If that means fighting with manufactured weapons, then so be it. Had He not asked to see you, you never would have gotten this close to the gates."
- The Lone Wanderer: "How do the Treeminders normally handle other Outsiders?"
Birch: "If the Outsider doesn't have His blessing, we simply deny him entry to our home. If they persist on trying to gain entry, or display any hostile act that could potentially harm the Great One, we take action. If the Outsider were a Raider or some other nefarious type, we ensure they don't report our location back to their comrades."
- The Lone Wanderer: "Which brings us to why I'm here, I suppose."
Birch: "Yes. Indeed it does. Sorry I don't speak to Outsiders very often and I tend to get lost in conversation. As you approached Oasis, He said you were coming and I was sent out to meet you personally with a request. He wishes to meet with you. You'd be the first Outsider to do so in a very long time."
The Lone Wanderer: "So what was all this about meeting someone?"
Birch: "Yes, my apologies. I don't speak to Outsiders very often and I tend to get lost in conversation. As you approached Oasis, He said you were coming and I was sent out to meet you personally with a request. He wishes to meet with you. You'd be the first Outsider to do so in a very long time."
- Fallout 3 Official Game Guide Game of the Year Edition p.319: "Oasis is a fertile, verdant dot in the center of all the desolation. This odd hidden vale is home to a strange, tribal-like people who call themselves the Treeminders. You are welcomed into Oasis with open arms, and their leader, Tree Father Birch, invites you to meet their god. Oasis is tucked away inside a giant rocky outcrop in the mountains just northeast of the monorail and freeway skeletons, and the entrance is close to a rope bridge."
- The Lone Wanderer: "Amazing, this place seems so abundant with animal life."
Birch: "The innocent creatures are drawn here by His gifts. They come from across the Wasteland to live in this sanctuary. This part of the world is healing, my friend, and it's all thanks to Him."
- There are sounds of birds, crickets and squirrels as background sounds in Oasis.
- Three Dog's dialogue: "Here's a question for all you faithful listeners. Have you guys and gals ever seen... a tree? No, no, no. Not those shriveled black things. I’m talking real trees. Brown bark, green leaves, photosynthesis, all that good stuff. Now what if I, the all-powerful Three Dog, were to tell you that somewhere right here in the Capital Wasteland, there’s a place with LOTS of trees. A veritable Oasis of green in that depressing sea of brown. Look, it was years ago, and I MAY have been experimenting with Jet at the time, but I’m telling you, it’s out there..."