Interesting info on Vervain

Vervain
Verbena officinalis
This Old World native was a favorite of the Druids, who gathered vervain when the Dog Star, Sirius, was on the rise, in the dark of the Moon. The Druids utilized vervain in divination, consecration, and ritual cleansing of sacred spaces. They made a magical drink called the Cauldron of Cerridwen (a shape shifter) that some say included rowan berries, sea water, lesser celandine, flixweed, and vervain, which brought the drinker creative energy for bardic song and prophecy; a drink made from vervain is still said to help poets in their work. Vervain is also still used to make a drink for initiating into Druidic paths. It is fragrant and can be drunk as a tea or burned as an incense. In its connection with the Underworld, it can be added to a cup of wine drunk on Samhain to aid contact with the Beloved Dead.
In Purification

Vervain has a long history of use in purification. King Solomon cleansed the Temple with vervain, and the Romans placed it on altars in honor of Venus and Diana. A lustral water can be made from vervain for purifying ritual tools, and a bath with vervain can help the bather prepare for ritual work. In the British Isles, people held vervain over the Beltane fire to protect their livestock and strewed it over their fields at Summer Solstice to make sure they would be fertile. Nowadays, Pagans strew it over their gardens for the same reason.

As Protective
However, vervain is also protective--Roman soldiers carried vervain with them into battle, and homes have been sprinkled with an infusion of vervain to keep out evil. It can also be burned as an incense for this purpose. In the old Langauge of Flowers, vervain stood for enchantment and still is very important in various aspects of magick. Drinking the tea is said to help in astral work and divination, and for that reason is tied by some to Mercury. A mug of vervain tea is made from 1-3 teaspoons of herb left to steep in a mug for 10-15 minutes. Also, you can make an oil to anoint the Third Eye by macerating this herb in olive oil.
Other Names
Vervain is also known as Vervan, Van, Ferfaen, Verbein, Verbena, Verbinaca, Dragon's Claw, Enchanter's Plant, Tears of Isis, Juno's Tears, Herba Veneris (herb of Venus), Persephonion, Demetria, Mercury's Moist Blood, Peristerium, Sagmina, Pigeon Grass, Pigeonwood, Frog-foot, Simpler's Joy, Altar Plant, Herba Sacra or Herbe Sacrée, Holy Plant, Herb of Cross, Holy Herb, and Herb of Grace.