Northern Prairie Wildlife Research Center
Northeast Wetland Flora
Field Office Guide to Plant Species
Polygonum hydropiper L.
- Family: Smartweed (Polygonaceae)
- Flowering: June-November
- Field Marks: The characters that distinguish this species from all other smartweeds are the
bristly leaf sheaths, the glandular-dotted, green and often purplish sepals, and the dull
(not shiny) achenes.
- Habitat: Wet ground.
- Habit: Annual herb with fibrous roots.
- Stems: Spreading to upright, branched or unbranched, often purple-red, up to 1 1/2 feet tall, smooth.
- Leaves: Alternate, simple, linear-lanceolate to ovate-lanceolate, pointed at the tip, tapering or somewhat rounded at the base, without teeth but often wavy-edged, smooth or sometimes short-hairy on the veins beneath, usually dotted, up to 3 1/2 inches long, up to 1 1/4 inches wide, short-stalked; sheaths fringed with short bristles.
- Flowers: Several in interrupted racemes, the racemes drooping or arching, up to 3 1/2 inches long.
- Sepals: 4, united below, greenish, often tinged with purple and bordered with white, dotted, up to 1/8 inch long.
- Petals: 0.
- Stamens: 4-6.
- Pistils: Ovary superior; style 2- to 3-parted.
- Fruits: Achenes lenticular to triangular, ovoid, dull, striate, dark brown to black, up to 1/6 inch long.
- Notes: The achenes are eaten by waterfowl.
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