Collecting Sassafrass for File'

Pick the leaves before the first cold snap, ideally the last full moon in August. The nutrients are still in the leaves then. Hang the branches to dry in a pillowcase on the line, or in a the cabanne, and at Thanksgiving, with the family all get together, clean out the twigs, crumble the leaves by hand, picking out the leaf stems. Then use a spice mill, blender or mortar and pestle to grind and then you can sieve it to make it a very smooth powder.
If a tree is not near, replant it before spring in the new location, before the budding begins, while it is still dormant. Usually you can find a few younger plants near the older, as the roots run, and offshoots develop.