When to use
You can use this method after the group have implemented their projects. While using it you can find out what kind of conflicts the group had. For example conflict between the group members, conflict with the society, or conflict with a different group.
How many people, how long
The group can be consist of any number. But it is better to do the evaluation with the whole group and not to separate them. You can only separate them into small groups /max 4 people/, when they need to think and remember about the conflicts that happened. For this they need 15 minutes. And for representing the stories 5 minutes.
What do we need?
For making a tree you need to draw a big tree on the wall, or you also can fix A3 paper on the wall and draw the tree on it. Then give the participants two different colours of stickers; one in a green rectangular form and another pink or red flower form. Ask them to write the result of the conflict on a pink or red paper and the reason of conflict on a green paper. Then fix the green paper on the roots of the tree, and the pink or red paper on the branches. Ask them to tell the conflict and the solutions, if the had or did before.
At the end
When you heard all the stories, give a feedback not on a concrete story, but about conflicts, what does it means, how is it important to have conflict situation, how is it important for the group development.