Comprehensive Description

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Description

This annual plant is about ½–1½' tall. It has stems that are unbranched or sparingly branched below, becoming more branched above; they are ascending to erect. The stems are light green, terete, slender, and glabrous to minutely pubescent. In addition, there are usually sticky patches along the stems between adjacent pairs of leaves; these sticky patches are often discolored and they may have dead insects, spider webs, and other debris clinging to them. The nodes of the stems, where pairs of leaves occur, are somewhat swollen and enveloped by short sheaths with membranous upper margins. Opposite leaves are sparsely distributed along the entire length of each stem, where they are sessile. These leaves are up to 2" long and 10 mm. across, although they are usually about one-half that size. The leaves are linear-lanceolate or linear-elliptic in shape, while their margins are entire (toothless) and minutely ciliate. The upper and lower surfaces of leaves are light green or light-medium green; they are glabrous to sparsely and minutely pubescent, except at their bases, where some white hairs occur. The leaves usually have conspicuous central veins, along which they are either flat or angled slightly upward. The upper stems terminate in small clusters of flowers (one floral cluster per stem); each floral cluster has relatively few flowers (typically only 2-4). The pedicels are up to 12 mm. (½" long), light green, terete, and slender. Each flower is about 4-5 mm. across, consisting of an open-ovoid calyx with 6 teeth, 5 small petals, 10 stamens, and a pistil with 3 styles. The petals are usually white, although sometimes they are pink or purple to a greater or lesser degree. Some plants produce bicolored petals that are white above and purple below, while other plants produce flowers that lack petals. These petals are obovate in shape and notched at their tips. A mature calyx is about 6-9 mm. long and about one-half as much across. Each calyx has 10 longitudinal ribs that are slightly elevated, angular-convex, and relatively thick; they are separated by narrow shallow furrows. The ribs of the calyx are often a slightly darker shade of green than the furrows; the calyx overall is light-medium green, glabrous, and sticky. The blooming period occurs from late spring to mid-summer, lasting about 1 month for a colony of plants. However, some plants may bloom later in the year in response to disturbance. The flowers are diurnal, opening up in response to bright sunlight. There is no noticeable floral scent. Mature seeds are less than 1 mm. in length, reniform (kidney-shaped), minutely bumpy across their surfaces, and black; they are distributed to some extent by the wind. The root system consists of a branching taproot. Reproduction is entirely by seeds. Cultivation

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© John Hilty

Source: Illinois Wildflowers

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