This adventive annual plant is about 4-12" tall, branching occasionally. The narrow round stems are covered with white hairs. The lower leaves are opposite, while the middle to upper leaves are alternate. These leaves are up to 1" long and 1/6" across. They are linear-oblong or linear-oblanceolate, with margins that are ciliate and smooth. From the axil of each middle or upper leaf, a single flower develops from a slender pedicel about 1" long. Sometimes a second flower develops from the leaf axil. Like the stems, these pedicels are covered with white hairs. The flowers are up to 1/4" in length. The corolla is tubular, with 5 spreading lobes in the front and a short spur in the back. The corolla has a small opening at the throat and is more or less two-lipped with 2 upper lobes and 3 lower lobes. It is variously colored, usually some shade of lavender, light purple, or white. Sometimes the corolla is bicolored, with the upper lobes lavender or light purple and the lower lobes white. There are usually a few hairs at the base of the lower lobes. The calyx is green or purplish green and quite hairy. It has 5 oblanceolate lobes that are almost as long as the corolla. The blooming period occurs during the summer and lasts about a month. There is no noticeable floral scent. Each flower is replaced by an ovoid capsule that contains numerous brown seeds. These seeds are tiny enough to be dispersed by gusts of wind. The root system consists of a slender taproot. This plant spreads by reseeding itself.