Northern Prairie Wildlife Research Center
Western Wetland Flora
Field Office Guide to Plant Species
Polygonum bistortoides Pursh
- Family: Smartweed (Polygonaceae)
- Flowering: May-August
- Field Marks: American bistort differs from all other species of Polygonum by its long-stalked basal leaves, its unbranched stem, and its thick, solitary, spike-like raceme.
- Habitat: Along streams, in wet meadows, particularly in the mountains.
- Habit: Perennial herb from a thick, fleshy rootstock.
- Stems: Upright, unbranched, up to 1 1/2 feet tall, smooth.
- Leaves: Basal and alternate, smooth, without teeth, the lowermost oblong to oblanceolate, pointed or rounded at the tip, up to 10 inches long, up to 2 inches wide, on stalks up to 8 inches long; uppermost leaves similar but sessile.
- Flowers: Many crowded into a terminal, solitary, cylindrical, spike-like raceme; raceme up to 3 inches long, up to 3/4 inch wide; flower stalk 1/8-1/3 inch long.
- Sepals: 5, united at the base, pink or white, petal-like, up to 1/4 inch long.
- Petals: 0.
- Stamens: Usually 5-9, exserted beyond the sepals.
- Pistils: Ovary superior.
- Fruits: Achenes triangular, pale brown, smooth, shiny, up to 1/6 inch long.
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