Mature plants are covered with short, stiff hairs. Stems are four-angled and unbranched or shortly branched. Leaves are numerous, opposite, and borne directly on the stem. They are long, narrow, and tend to be a yellowish green in color. Venation is pinnate.
Inflorescences are a group of one to eight flowers on unbranched flowering stalks.
Corollas are rose to lavender with two yellow lines and red spots inside. The petals are fused into a bell shaped tube with five short lobes. The upper two limbs are slightly longer and over arch the lower three, creating a weakly bilateral shape. The four stamens are covered with silky hairs. The upper two stamens are shorter than th e lower two.