[header] How to make a rooting tonic [title] Collect approximately 2 cups of willow branches or 3 cups of bark. [substeps] Choose small, young branches that are no thicker than a pencil. The highest concentration of hormone exists in the youngest branches. 
You can also use bark from live older willow branches or trunks. If you go this route, you need to use more bark because it contains less hormones.