Describe three characteristics that trees used to build treehouses should have. why are these characteristics essential

Three characteristics that trees used to build treehouses should have are:
- trees should be part of a long-lived hardwood. This is important in order maximum support  to be achieved. 
- trees should have load-bearing branches at least 8 in. in diameter , also for better support
- trees should be  mature, healthy and strong. . Healthy and strong trees are more stable and supportive. 
The reason for the all mentioned characteristics is the safety.