|smartweed, knotweed (Polygonum spp.)||
smartweed and knotweed (Polygonum spp.; SMARTWEED FAMILY [Polygonaceae]) More than 30 species of weedy annual or perennial plants with very small flowers of 5 white to pink, petal-like sepals, growing in spikes or spikelike branches, or in the leaf axils. The stems are jointed, with a membranous sheath above each joint. The numerous Wisconsin Polygonum species are often trailing plants, rarely showy, and are common along roads or in moist or wet open places. Flowers in summer and early fall. 
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