Memento Stick~Tutorial how to make a journey stick with children on a nature walk: a great activity for children to learn about nature and their environment.
Stick-Star Garden Mobile - Fun & Easy Nature Craft for Kids - Happy Hooligans
Use clay to create a sculpture attached to a tree. Have the kids hunt for leaves/twigs/grass (natural items) to add to the sculpture.
Forest Craft: How to make a stick picture frame
Make a natural loom from a tree stump! Just bring string out to the yard.