I teach this project to teach kids how to overlap to create depth, to blend common colors on the wheel, how to use watercolor pencils, and the anatomy of a leaf.
I have a collection of card stock leaf stencils that I made from real leafs for the students to trace onto the paper. We use 12 by 18 inch paper that is medium to heavy weight to allow for water. Students trace leaves with pencil, draw in the veins of the leaf, then outline with permanent black marker.
I then take all students to the back when they are ready for coloring to demonstrate the proper use of watercolor pencils. I use the color wheel to show them what kind of colors should be blended as well as what kind of colors should be next to each other (opposites or complements) to avoid visual flatness. They use the pencils lightly on each leaf. Each leaf should contain at least 2 colors (to show blending of color knowledge). These pencils are NOT colored pencils (only look similar), so they do not need to be used as such.
After all leaves are colored, students use a medium to small size brush to blend the two colors on each leaf together. Each leaf should be blended individually. Do not use water and brush in one continual sweep over paper. Blending all colors on the page together at one time will result in a muddy color (neutral) appearance.
After water is used t blend each leaf, I have the students do the last stem.
They can use colored pencils or markers to pop out the outside line and veins visually. This seems like an unnecassary step, but you would be surprised at how they come to life after this.