Every plant has its own kind of leaves. On a recent author visit to Ecole Bilingue in Berkeley, California, I saw some wonderful art projects inspired by leaves that the children had collected. Using different colored pens, the students followed the edges of the leaf, making a series of outlines and creating beautiful designs. Each piece of art was unique, just as the leaves are in nature.
This would be a great activity to do in the fall when leaves are turning colors. But it could be done at any time of year when trees are full of leaves.