Blue vervain (Verbena hastata) and white vervain (V. urticifolia) are american native perennials. Other vervain species, mostly European natives, are now widespread across most of the United States and Canada.
Vervain is an herb that has not been well studied, but it does have a long history of use. Although once attributed with magical properties (granting love and bestowing immortality) and used as a panacea to treat a wide variety of ailments, these days vervain is mostly used as a relaxing nervine.
It is restorative to the nervous system and calms stress, anxiety, and restlessness. It relaxes and uplifts the mood. Stress sometimes comes with an upset stomach or headache; vervain soothes and promotes digestion, improves the appetite, and is helpful in the treatment of stress headaches. This relaxing effect makes it useful in cases of restless insomnia.
Research has verified that blue vervain has anti-inflammatory and pain relieving (analgesic) effects, similar to aspirin.  Vervain is also a gentle astringent which has found use as a mouthwash for for sore, inflamed, or bleeding gums, and as an eyewash for tired, inflamed eyes. Its astringency combined with its antispasmodic properties makes it helpful for IBS, as well as for coughs or asthma. It has a positive effect on the liver.
Vervain helps encourage sweating and regulate fever. Its positive mood benefits make it a great pick-me-up while recovering from an illness. It balances hormones and normalizes thyroid function. It is useful for menstrual complaints including hormonal headaches, and as a tincture to cool menopausal hot flashes.
Vervain contains the glycoside verbenin, which is believed useful as a galactogogue, to increase milk production in nursing mothers.
Vervain is bitter but the leaves and flowerheads can be used alone or with other herbs in a tea. Vervain’s effects blend well with chamomile. I have used the leaves of blue vervain with the flowers of goldenrod and mullein (for a headache), and found the tea quite pleasant tasting. The seeds are edible.
Vervain is not meant to be used in high doses. In higher doses, it has been used as an emetic (to induce vomiting.) Vervain can be stimulating to the uterus and should not be used during pregnancy; however, it has been used during childbirth to help labor contractions.
More identification photos for blue vervain: Minnesota wildflowers
Other species of vervain:
1. Good health herbs