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DescriptionThis perennial plant is 1-4' tall and usually unbranched, except sometimes at the base. The central stem is light green, short-pubescent, and 4-angled with shallow vertical grooves. At intervals, there occurs pairs of opposite leaves that become slightly shorter and more narrow as they ascend the stem. Each pair of leaves rotates about 90° from the pair of leaves either immediately above or below. The leaf blades are 1-3" long, 1/3-1½" across, and flat; they are ovate to oblong-lanceolate in shape and their margins are dentate to sparsely crenate. The upper surface of each leaf blade is medium green and sparsely short-pubescent, while the lower surface is slightly more pale and pubescent (at least along the central veins). On each leaf blade, there are usually 2 lateral veins that run parallel to the central central and a few secondary veins that branch from the central vein along its length. The petioles of the leaves are ¼-¾" long. The lowest leaves, which are wider, are often withered by the time that flowering occurs. The flowers occur in dense axillary clusters along the upper half of each stem; these floral clusters are whorled and sessile. Individual flowers are about ¼" long and 1/8" across, consisting of a 2-lipped tubular corolla with 4 lobes, a calyx with 5 teeth that have spine-like tips, 4 stamens, and a pistil with an ovary that is divided into 4 parts. The corolla is white to pink and softly short-hairy along the exterior of the upper lobe, which functions as a protective hood. There is also a rounded lower lobe and two smaller lateral lobes. A patch of red occurs within the throat of the corolla. The calyx is light green, sparsely canescent along its exterior, and 5-veined. The corolla of the flower is about the same length as the calyx (including the tips of its teeth) or a little longer. The blooming period occurs from early summer to early fall for about 2-3 months. Usually, only a few flowers are in bloom at the same time across several floral clusters. Each flower is replaced by a cluster of 4 small nutlets during the fall. Individual nutlets are oblongoid and 3-sided. The root system is fibrous and rhizomatous. Vegetative colonies of plants are often formed from the rhizomes.