Northern Prairie Wildlife Research Center


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Aquatic and Wetland Vascular Plants of the Northern Great Plains

13. Amaranthaceae, the Pigweed Family

1. Amaranthus L. -- Pigweed

2. Amaranthus tuberculatus (Moq.) Sauer -- Tall water hemp

Similar to the preceding, erect to spreading, usually much branched, 0.2-1(2) m tall, glabrous to rarely sparsely puberulent above, green or slightly tinged with purple. Leaves variable, the larger ones with blades ovate to lanceolate, 4-10 cm long, the smaller with blades oblong to spatulate, 1-4 cm long; petioles short to as long as the blade. Inflorescence of usually many simple, terminal and axillary spikes, and with some axillary clusters. Bracts 1-1.5 mm long, slender with the midrib excurrent in the male, strongly excurrent in the female; male flowers with 5 sepals, these nearly equal, 2.5-3 mm long, the inner ones obtuse to emarginate, the outer acuminate, the midvein not excurrent; stamens 5; female flowers without sepals or rarely with 1-2 rudimentary sepals. Utricle 1.5-2 mm long, splitting irregularly, without a distinct line of dehiscence, smooth or usually irregularly tuberculate; seed reddish-brown to black, 0.8-1 mm in diameter. Jul--Oct. Same habitats as the preceding; scattered; (VT to ND, s to NJ, OH, AR and NE). Acnida altissima Riddell.
GIF- Distribution Map

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