Inedible or rarely eaten parts of the garlic plant include the "skin" and root Cluster.

http://en.wikipedia.org/wiki/Garlic

Inedible or rarely eaten parts of the garlic plant include the "skin" and root cluster. The papery, protective layers of "skin" over various parts of the plant are generally discarded during preparation for most culinary uses, though in Korea immature whole heads are sometimes prepared with the tender skins intact.The root cluster attached to the basal plate of the bulb is the only part not typically considered palatable in any form.