I've actually used the friendship tree in many other areas of the curriculum. I teach a reception class at a special needs school in the UK so some of the concepts in the unit are not yet appropriate but most aspects are very adaptable. I have used the trees as a reward system. The 'learning trees' are on a big diaplay board on the wall, they have branches, each branch belongs to one child. The branches have leaves on them with the child's face. Some leaves have statements on them (targets/goals). They receive a leaf everytime they reach a target or do something special. These leaves get sent home and the parents stick them in our 'learning tree' scrapbook. Most leaves are sent home with a picture of the child engaged in the targeted activity.