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Aquatic and Wetland Vascular Plants of the Northern Great Plains

13. Amaranthaceae, the Pigweed Family

1. Amaranthus L. -- Pigweed

1. Amaranthus rudis Sauer -- Water hemp

Plants erect with ascending branches, 0.5-2 m tall, or often low and spreading with branches 1-5 dm long, glabrous or nearly so, green or sometimes the stems and inflorescences strongly purple. Leaves oblong-lanceolate to ovate-lanceolate or rhombic-oblong, 3-10 cm long, obtuse to rounded or sometimes notched at the tip, attenuate at the base, reduced to bracts upward in the inflorescence; petioles mostly 0.5-4 cm long. Inflorescence of usually many terminal and axillary spikelike branches, or some of the lateral branches merely short clusters. Bracts 1.5-2 mm long, with a shortly excurrent midrib in the male, a conspicuously excurrent midrib in the female; male flowers with 5 sepals 2.2-3 mm long, the outer longer than the inner and with midveins excurrent into a mucronate or aristate tip; stamens 5; female flowers with 1 or 2 sepals, when 2, one of the sepals rudimentary or less than 1 mm long, the longer (or single) one ca. 2 mm long. Utricle 1.2-1.6 mm long, circumscissile, with a distinct line of dehiscence around the middle, the top coming off like a lid, often with faint ridges of tubercles on the top portion; style branches 3-4; seed reddish-brown to black, 0.9-1.1 mm in diameter. Jul--Oct. Shores, stream banks, mud and sand bars and low places in fields where sometimes weedy, frequent in e SD and NE, less common w and n; (WI to ND, s to LA and TX, adventive elsewhere). Acnida tamariscina (Nutt.) Wood, Amaranthus tamariscinus Nutt.
GIF-Amaranthus rudis
Amaranthus rudis.
GIF- Distribution Map

Map key

Return to Family -- Amaranthaceae - The Pigweed Family
Next Species -- Amaranthus tuberculatus (Moq.) Sauer -- Tall water hemp

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