Botanical name: Persicaria sinuata Family: Polygonaceae (Knotweed family)
Synonyms: Polygonum sinuatum, Cephalophilon sinuatum
Red-Stem Knotweed is a prostrate, 15-45 cm long, hairless, branched, annual herb, with slender, striped, brownish, or reddish stems, rooting at nodes. Leaves are stalked pinnately lobed, 0.8-4.5 x 0.75-2.0 cm, inverted-lanceshaped, blunt, lobes 2-4, end lobe triangular, hairless. It is often confused with Lobed Leaf Knotweed. Ochrea 0.5-1.25 x 0.25-0.75 cm, ovate, entire shortly fringed with hairs, tubular. Flowers are borne in compact spherical heads at branch-ends, carried on flower-cluster-stalk 1.8-5.0 cm long, hairless or very sparsely hairy just below the head, head 5-7 mm in diameter. Ochreolae 0.15-0.4 cm long, tubular, entire. Flowers are nearly stalkless to stalked. Tepals are 5, pink, biseriate, unequal, 1.25-1.5 x 0.75-1.0 mm, obovate, blunt. Stamens are 5-8, biseriate, protruding, filaments unequal; anthers basifixed. Red-Stem Knotweed grows on higher altitudes between 2500-3000 m in the Himalayas, near water courses. Flowering: August-September.
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The flower labeled Red-Stem Knotweed is ...