Believed to be a common medium used for enchanting others.  The leaves would be spelled and gifted to someone who then would be the target of the enchantment.  The leaves made an innocent-looking home for something that could be harmless or could be devastating.

They can also be used for enchantments which allow you to detect magick or detect someone of magickal prowess as the leaf can give off a powerful odor or discolor itself when near magick.