Rue, Ruta graveolens, is a blue-green shrubby herb of the Mediterranean with a strong, bitter, acrid scent, long grown in physic and cottage gardens. Its enduring English name is the herb of grace, or herb-grace, for a bunch of rue was used to sprinkle holy water in the rite of blessing before Mass, so that the plant of bitterness became the plant of benediction. That double sense runs through its lore: rue, to feel regret, and rue the plant were felt to belong together, and Shakespeare's Ophelia gives rue as the herb of sorrow and repentance, wearing it herself with a difference.
In the ancient world rue was a genuine kitchen herb as much as a magical one: the Roman cookbook attributed to Apicius calls for it repeatedly as a pungent seasoning, and the Romans are credited with introducing the plant to Britain, where it later became better known for magic and medicine than for the table. It survives today as a culinary herb chiefly in a few specific regional cuisines, including parts of Ethiopian and northern Italian cooking, where a single leaf is sometimes used to flavour grappa or a local liqueur, a small, geographically scattered survival of a taste most of Europe abandoned centuries ago.