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DescriptionThis perennial plant is about 2' tall, often branching near the base. The stems are pale green, terete, and usually hairless. The opposite leaves are up to 2½" long and ¾" across, sessile against the stems, and pale green to grayish green. They are usually oblanceolate, but sometimes lanceolate or elliptic. Their margins are smooth and slightly ciliate, otherwise the leaves are hairless to sparsely pubescent. Some of the upper stems terminate in large panicles of numerous flowers. Each flower is ½-¾" across and ¾-1" long, consisting of 5 white petals that are deeply cleft (resembling 10 petals), a bladder-like calyx that is pale green to dull pink, 10 exerted stamens, and a pistil. The lobes of the cleft petals are narrowly oblanceolate. The swollen calyx is ovoid, hairless, and about ¾" in length; it has 20 longitudinal veins across its surface that are connected by a reticulated network of smaller veins. Compared to the calyx, the veins are a deeper shade of green or pink. The upper rim of this calyx has 5 broad triangular teeth. While in full bloom, the entire plant has a tendency to lean over to one side because of the weight of the flowers. The blooming period is usually early to mid-summer, and it lasts about 1-2 months. Each flower is replaced by an ovoid capsule that is open at the top; it contains small brown seeds. The root system consists of a taproot with short rhizomes. This plant can spread vegetatively.