This is a very valuable plant. The root is the part we use in medicine. It should be dug in July or August.

Medical properties and uses. -- Vervain is a fine tonic, in small doses, to follow all forms of fever with during convalescence. In large doses it is an emetic, but should never be taken to that extent. It is a very valuable bitter tonic. To prepare it for bitters, fill a bottle half full of finely-chopped root, and then fill with good whisky. Dose, a teaspoonful three times a day. The root is best when green.