In the series of young adult novels The Vampire Diaries, author L. J. Smith uses vervain to protect humans from vampires. Humans can ingest the herb to protect their blood or wear it to ward off compulsion. In the television adaptation vervain not only protects a human from compulsion by vampires, it also physically harms vampires. When applied directly to their skin it burns similar in effect to holy water on a demon. L.J. Smith however didn't make this herb and its supernatural effects up, it has long been used in folklore.
Vervain, also called Verbena is a genus in the family Verbenaceae.
The leaves are usually opposite, simple, and in many species hairy, often densely so. The flowers are small, with five petals, and borne in dense spikes. Typically some shade of blue, they may also be white, pink, or purple.
Vervain has long been associated with divine and other supernatural forces. It was called "tears of Isis" in ancient Egypt, and later on as "Juno's tears". In ancient Greece it was dedicated to Eos Erigineia.
In the early Christian era, folk legend stated that Verbena was used to staunch Jesus' wounds after his removal from the cross. It was consequently called "holy herb" or "Devil's bane".
Vervain flowers are engraved on cimaruta, Italian anti-bewitching charms. In the 1870 The History and Practice of Magic by "Paul Christian" it is employed in the preparation of protective charms.