While the common vervain has flowers that are typically some shade of blue, the True Vervain or Imperial Vervain is known for tight clumps of tiny yellow-green flowers. It is recognised by its brilliantly green, excessively hairy leaves which release a delicate, fresh aroma when crushed or bruised. These leaves are carefully gathered, dried and prepared to release their powerful healing qualities. The aromatic juice of the crushed leaves and stems is held to have a calming, relaxing effect when added to boiling water and the steam inhaled. Overuse may result in stomach ache, apathy, and a feeling of mental dullness or mild depression. Small quantities, when mixed with soda crystals can also provide relaxing bubbles for bathing.

Properly applied, True Vervain heals a target to full hits if applied while the wounds are being dressed by a skilled physician.