Vervain was known in many legends as one of the herbs sacred to the Druids. Although it is often associated with the Summer Solstice, the vervain plant is highly potent in late summer, around the time of Lammas.
In Hoodoo and other folk magic traditions, vervain is used to make Van-Van oil - this is simply a blend of vervain and a base oil, simmered and strained. This oil is used to provide magical protection, and clear away evil energies. In many forms of folklore, vervain is associated with workings that decrease lust - however, the scent of vervain is a well-known aphrodisiac.
In addition to matters of the libido, however, vervain is commonly incorporated as a cleansing herb. You can brew up a batch of vervain water to cleanse your magical tools, asperge around a sacred space, or purify your altar for ritual....
... I am so sorry, but this post has been combined with another, and moved to my new website, the Magickal Apothecary. It can be found here: Vervain Magick and Lore