White vervain has opposite, simple leaves on thin, rigid, green stems. The leaves look similar to those of Urtica, which is the reason for the plant being named urticifolia. The small flowers are borne in spikes; they open in summer and unusually for this normally bluish-flowered genus are white. The fruit is a dark- colored capsule with many brown and thin seeds. The entire plant except for the flowers and fruit is covered in stiff bristles.