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Montana Field Guides

Scarlet Ammannia - Ammannia coccinea

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Not Documented

Global Rank: G5
State Rank: SNA
(see State Rank Reason below)

Agency Status


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State Rank Reason (see State Rank above)
Ammannia coccinea is not documented in Montana (MTNHP Status Review in 2017). Ammannia coccinea was included in the Flora of Montana (Booth 1966). Ammannia coccinea was treated as a synonym for Ammannia robusta which was included in the Vascular Plants of Montana (Dorn 1984). Ammannia coccineaand Ammannia robusta have similar appearances, which have led to mis-identifications. It has been Ammannia robusta that has been overlooked in floristic surveys (Graham 1985). A conservation status rank is not applicable (SNA) because this plant is not known to occur in Montana.
General Description
This excerpt is adapted from A Revision of Ammannia (Lythraceae) In the Western Hemisphere (Graham 1985).

PLANTS: Annual herbs up to 1 meter tall, unbranched or with short branching above its base.

LEAVES: Opposite arrangement. Blades are linear-lanceolate to linear-oblong, rarely elliptic to spathulate. Largest leaves 20-80 mm by 2-15 mm. Apex is acute, base is auriculate to cordate, clasping, or occasionally cuneate.

INFLORESCENCE: Flowers arranged in cymes that arise from leaf axils. Flowers are usually 3 or more per cyme. Petals are deep rose-purple. Anthers are dep yellow. Fruits are 3.5-5 mm in diameter.

Potential specimens should be provided to and verified at one of our State Herbaria:
University of Montana (MONTU), Montana State University (MONT), or Montana State University-Billings (MSUB).

Flowering and fruiting after water recedes; usually August.

Diagnostic Characteristics
In the North American flora Ammannia robusta has been overlooked because of its morphological similarity to Ammannia coccinea (Graham 1985).

Ammannia coccinea - Not Documented in Montana
*Leaves: Sessile and opposite.
*Inflorescence: Cyme with short to long peduncles, rarely completely sessile. Usually 3 or more flowers per leaf axil (cyme).
*Petals: Deep rose-purple.
*Anthers: Deep yellow.
*Fruits: 3.5-5.0 mm in diameter.

Ammannia robusta - Scarlet Ammannia, SOC
*Inflorescence: Cyme is sessile. Usually 1-3 flowers per leaf axil (cyme).
*Petals: Pale lavender, occasionally deeper purple veined.
*Anthers: Yellow.
*Fruits: 4-6 mm in diameter.

Rotala ramosior - Toothcup, SOC
*Leaves: With short petioles and opposite.
*Flowers: 1 per leaf axil.

Some species of Epilobium have opposite leaves, 4-parted flowers, and occur in wet sites; however, their petals and sepals are borne on top of the ovary rather than surrounding it, and the fruits are long and slender.

Species of Gratiola, Bacopa, and Veronica all have opposite leaves, but their flowers are larger and have a united corolla.

Range Comments
In the United States, Ammannia coccinea occurs in California, the mid-western States, and portions of the eastern States, but it has not been found in Montana. Where the ranges of Ammannia robusta and Ammannia coccinea overlap both species could be present at a single site (Graham 1985).

Drying mud around shallow ponds and other wet areas in the valleys and plains.

  • Literature Cited AboveLegend:   View Online Publication
    • Dorn, R. D. 1984. Vascular Plants of Montana. Cheyenne, WY: Mountain West Publishing. 276 pp.
    • Graham, S. 1985. A Revision of Ammannia (Lythraceae) in the Western Hemisphere. Journal of the Arnold Arboretum 66: 395-420.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Blankinship, J. W. 1905. Supplement to the flora of Montana: Additions and corrections. Montana Agricultural College Science Studies - Botany 1(2):1-109.
    • Booth, W. E. and J. C. Wright. 1966. Flora of Montana-Part II: dicotyledons. Montana State University, Bozeman, MT. 305 pp.
    • Heidel, B. 1994. Potential impact of proposed noxious weed treatment at Bluewater Fish Hatchery (MDFWP) on plant species of special concern. Unpublished report to Gary Shaver, Bluewater Fish Hatchery. Montana Natural Heritage Program, Helena, Montana. 5 pp.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
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Citation for data on this website:
Scarlet Ammannia — Ammannia coccinea.  Montana Field Guide.  .  Retrieved on , from