I see nature crafts as crafts that you actually do with materials from nature. These activities are quite common but, definitely fit the bill.
The first one is a leaf rubbing activity. The children collect leaves, lie them on the table, place a piece of paper over the leaves and then either with one or more crayons (with paper off) rub over the leaves.
The second one uses leaves as well. This time the children use the leaves along with an assortment of other materials like googly eyes, craft sticks, pom poms etc for them to make leaf people.
The third uses leaves as well. Find the largest leaves you can, and have the children paint them and then collage with them.
They can even cut them up if they like. (for the leaves above I used acrylics as they stayed on the best)
The fourth and fifth activities are to make items out of clay.
For exact directions on how to make these clay pots and necklaces see the clay projects for kids post.