Before starting-- Talk about the life cycle of trees, the seasons, the parts of the tree { bark,
sap, leaves, branches, etc.}, and / or how a tree grows.
Plan out how you will make the tree.
Talk about the materials you will need and use.
During-- Talk about the how the past feels
Have the children describe what they are doing, do they like the way the paste feels?
Have them talk about the process -- how the tree has changed from begining through the end.
Talk about why each layer needs to dry
Ask them how they want to do each step.
Remember this is their project and you are only helping.
These are only suggestions to get you started.