Blue Vervain is edible and medicinal. Vervain had many uses in Native American culture as food and medicine. The seed are edible when roasted and are ground into a powder and used as a piñole (an Indian flour). 
The leaves and roots of Blue Vervain are a valuable alternative medicine used as an  antidiarrheal, analgesic, anthelmintic, antiperiodic, astringent, diaphoretic, emetic, emmenagogue, expectorant, sedative, tonic, vermifuge, vulnerary. It is useful in intermittent fevers, ulcers, pleurisy, scrofula, gravel, easing pain in the bowels and expelling worms. A very strong infusion is emetic. As a medicinal poultice it is good in headache and rheumatism. An infusion of the plant is a good galactagogue (increases breast milk) and used for female obstructions, afterpains and taken as a female tonic.  
The infusion is used to help pass kidney stones and for infections of the bladder. Used as a sudorific and taken for colds and coughs. Also useful for insomnia and other nervous conditions. Recent medical research has detected the presents of adenosine, aucubin, beta-carotene, caffeic-acid, citral, hastatoside, lupeol, ursolic-acid, verbenalin, verbenin, and other chemical constituents in this plant which prove these uses to be valid. But much more research needs to be done on this herb and its constituents. It may prove to be useful in treating many cancers and other diseases.