Northern Prairie Wildlife Research Center
Nuttall's Waterhemp (Amaranthus rudis)
- Family: Pigweed (Amaranthaceae)
- Flowering: July-October.
- Field Marks: Species known as water hemps differ from all other species of Amaranthus by having the male and female flowers borne on different plants and by having 0-2 sepals for each female flower. This is the only water hemp with a completely dehiscent fruit.
- Habitat: Cultivated fields, banks of streams, edges of ponds and lakes, mud flats, sloughs.
- Habit: Stout annual herbs with fibrous roots.
- Stems: Erect, sometimes branched, smooth, up to 4 1/2 feet tall.
- Leaves: Alternate, simple, oblong to oval, rounded at the tip, tapering to the base, smooth, without teeth, up to 4 inches long; leaf stalks slender.
- Flowers: Crowded into slender, terminal spikes, green, the male and female flowers on separate plants.
- Male Flowers: Sepals 5, green, up to 1/6 inch long; pointed at the tip; petals 0; stamens 5.
- Female Flowers: Sepals 0-2, green, pointed; petals 0; ovary superior.
- Fruits: Ovoid, greenish, smooth, subtended by a shorter bract, dehiscent, with small spherical seeds.
- Notes: Waterfowl eat the seeds of this species. This water hemp can be the cause of hay fever in late summer. This species has been known as A. tamariscinus.
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