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This adventive plant is a summer annual about 1½–3' long; it branches occasionally, especially near the base. The stems are erect, ascending, or sprawling (often the latter); they are light green, more or less white-mealy, and terete or angular. The larger stems often have white longitudinal veins. The lowest leaves are opposite, while the remaining leaves are alternate; they have slender petioles up to 1" long. The leaf blades are up to 3½" long and ¾" across, becoming gradually smaller as they ascend the stems; they are green, flat, and either smooth or slightly undulate along their margins. The leaf blades have different shapes, but they are usually lanceolate-ovate, lanceolate, or oblong-linear; some leaves may have 1 or 2 lobes toward the base of their blades. The upper surface of each blade is hairless or glabrous, while the lower surface is often white-mealy. The upper stems terminate in spikes or spike-like panicles of flowers; axillary spikes also develop from some of the upper leaves. The flowers are arranged in sessile clusters along the spikes or the branches of the panicles. Common Orach is monoecious with separate male (staminate) and female (pistillate) flowers on the same plant. Each male flower has 5 sepals and 5 stamens; it is whitish green and about 1/8" (3 mm.) across. Each female flower has an ovary with 2 styles and a pair of small bracts at its base; it is green and about 1/8" (3 mm.) across. The male flowers lack petals, while the female flowers have neither petals nor sepals. The flowers and branches of each inflorescence are white-mealy. The blooming period occurs during late summer into the fall. Pollination is by wind. The bracts of the female flowers enlarge in size, becoming triangular-hastate in shape and about 1/5" (5 mm.) in length; they form a flattened fruit that encloses the developing seed. Mature seeds are flattened, circular, and shiny black; each seed is covered by a thin rough membrane that is difficult to remove. The root system consists of a branching taproot. This plant spreads by reseeding itself.


Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© John Hilty

Source: Illinois Wildflowers

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