Northern Prairie Wildlife Research Center
Rough Sumpweed (Iva annua)
- Family: Aster (Asteraceae)
- Flowering: July-October.
- Field Marks: Species of Iva differ from species of Ambrosia, the ragweeds, by having all the flowers the same, as opposed to ragweeds that have pollen-producing flowers in elongated spikes and pistil-producing flowers in short clusters in the axils of the leaves. Rough sumpweed differs from other species in the genus by its rough-hairy leaves.
- Habitat: Wet meadows, along streams, around ponds and lakes, fallow fields, wet prairies, roadsides.
- Habit: Annual herb with fibrous roots.
- Stems: Erect, branched, hairy, up to 6 feet tall.
- Leaves: Opposite, simple, ovate, pointed at the tip, tapering to the base or truncate, toothed, hairy, up to 5 inches long, up to 3 1/2 inches broad.
- Flowers: Many in small heads with several heads arranged in a group of crowded racemes up to 6 inches long, each head up to 1/6 inch long, subtended by narrow bracts.
- Sepals: 0.
- Petals: 5, united below into short tubes, cream-colored.
- Stamens: 5.
- Pistils: Ovary inferior.
- Fruits: Achenes dark brown, somewhat triangular, flattened, about 1/10 inch long.
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