You might cutting down a tree or two, when you notice something popping up from the ground. Yes its a evil tree and you can nuture it into a fully grown evil tree.
And yes you do need requirements.
It's best to have completed Tree gnome stronghold so you can access the spirit trees, you can ask them about clues so you can locate the evil tree. If the evil tree is fully matured the spirit tree will teleport you directly to it.
Runescape Evil Tree Requirements
Most important you can only kill two trees everyday, and a tree will appear every 2 hours.
Don't worry if you don't have supplies a leprechuan always is next to the evil tree cheering you on, he will supply you with everything you need to kill the evil tree.
As you go on battling with the tree you will recieve exp im not sure how much yet so as soon as i find out i will update this guide.
When the tree has finally been defeated you will gain rewards, these rewards range from money, logs(of the trees kind), money, nests and clue scrolls. Also the leprechuan will take any logs you recieve while woodcutting and put them in your bank ONLY! when your inventory is full.
I hope this guide was useful it is my first ever guide
Working as a clan
The easiest method I can think of is everyone has their own world and get into contact with a spirit tree and ask for any information about up coming evil trees, once someone has been notified about it they can then pass on the information to the rest of the clan about the world and location of the evil tree.