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Statewide IPM Program, University of California

Redstems  (Ammannia spp.)

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Life stages of Redstems seedling flowers mature plants flowering stem seeds fruit

Redstems, which include purple ammania, Ammania robusta, and other Ammania species are aquatic, broadleaf annuals that reproduce by seed and emerge through the water’s surface. In rice, they thrive where the stand is thin and do especially well during warm years.


Cotyledons (seed leaves) are triangular and dark green. The first pair of true leaves is oval or triangular. Leaves are opposite to one another along the stem.

Mature plant

Plants range from 5 to 30 inches (12.5–75 cm) tall. Stems are square in cross-section and branch extensively. Leaves are long, narrow, stalkless, and are opposite to one another along the stem.


Flowers are small, four petaled, bright rosy red, and grow in groups of three to four where the leaf stalks meet the stem.

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