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DescriptionThis perennial wildflower forms arching stems about 3-8' long that are unbranched or sparingly so. The base of each stem is spongy and swollen if it is submerged in water, otherwise it is more constricted and angular. Each stem is pale green to red and either glabrous or pubescent; it tends to be slightly woody at the base, but dies down to the ground each winter (at least in the Midwest). Both opposite leaves and whorls of 3 leaves can occur along the stems; they are up to 6" long and 1½" across. The leaves are elliptic in shape and smooth along their margins. The upper leaf surface is medium to dark green and glabrous, while the lower surface is pale to medium green and either glabrous or pubescent. The leaves taper gradually into short petioles (¼" or less) and long narrow tips. Clusters of non-terminal flowers occur in the axils of the leaves. Individual flowers are up to 1" long and 1" across, consisting of 5 wrinkled purple petals, a short tubular calyx with 5 primary teeth alternating with 5 secondary teeth, 10 stamens of varying lengths, and a pistil with a style. Sometimes there are more calyx teeth and fewer stamens. The bell-shaped calyx is light green to cream-colored with rose tints; its primary teeth are ovate, while its secondary teeth are elevated above the primary teeth and they are linear. The slender secondary teeth are often contorted or crooked and they are ciliate along their margins. The pedicels of the flowers are light green, glabrous or pubescent, and short (about ¼" in length). There are 2 or more leafy bracts underneath each cluster of flowers; they are up to ¾" in length and lanceolate to ovate in shape. The blooming period occurs from mid-summer to early fall, lasting about 1-2 months. Each flower typically lasts only 1-2 days. During the fall, the flowers are replaced by globoid seed capsules about ¼" across. Each capsule contains many chunky seeds; the seeds probably float on water. This wildflower reproduces vegetatively whenever its stem tips touch moist ground, where new plants will take root. As a result, colonies of vegetative plants often form.