Northern Prairie Wildlife Research Center
Arrow-leaved Tear-thumb (Polygonum sagittatum)
- Family: Smartweed (Polygonaceae)
- Flowering: June-October.
- Field Marks: This climbing Polygonum has arrowhead-shaped leaves and downward-pointing prickles on its stem.
- Habitat: Swamps, along streams, marshes.
- Habit: Annual climber with fibrous roots.
- Stems: Sprawling or climbing, with numerous stiff, downward-pointing hairs.
- Leaves: Alternate, simple, narrowly arrowhead-shaped, pointed at the tip, with a pair of pointed lobes at the base, smooth, up to 3 inches long.
- Flowers: Up to 12 in small, rounded clusters, pink or white.
- Sepals: 5, pink or white, free from each other.
- Petals: 0.
- Stamens: Usually 5.
- Pistils: Ovary superior.
- Fruits: Achenes triangular, black-brown, shiny.
- Notes: The downward-pointing hairs on the stem are stiff enough to break the skin. This species does not occur in region 8, despite the listing in the National Wetlands Inventory list.
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