It is an annual herb producing a hairy, erect stem 4 to 27 centimeters tall. The linear to nearly oval leaves are each up to 3 centimeters long and arranged in oppositepairs about the stem. The tubular base of the flower is surrounded by a reddish-green freckled calyx of sepals with small, pointed lobes. The flower corolla is one to two centimeters long and divided into two lips. These vary in color but often the upper lip is white and the lower is yellow. The upper lip has two lobes and the lower has three. Each lobe has two sub-lobes at its tip.