Ammannia coccinea (Valley Redstem)

Plant Info
Also known as: Scarlet Toothcup, Purple Ammania
Genus:Ammannia
Family:Lythraceae (Loosestrife)
Life cycle:annual
Origin:native
Habitat:sun; river banks, mudflats
Bloom season:July - September
Plant height:8 to 24 inches
Wetland Indicator Status:GP: OBL MW: OBL NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 4-petals Cluster type: whorled

[photo of flowers] Tight cluster in the opposite leaf axils all along the stem, with 1 to 5 flowers per axil, typically only 1 flower in an axil open at a time. Clusters have a very short stalk and individual flowers are stalkless or nearly so. Each flower is ¼ inch across or less, has 4 (rarely 5) pink to purplish, wavy petals with 4 yellow tipped stamens surrounding a stout green style in the center. The petals quickly wither away the day they open. The calyx tube is cylindrical, about 1/8 inch long with conspicuous ribs both mid-sepal and between them, the sepal lobes shallow and broadly triangular with an abruptly pointed tip. Where the sepal edges meet is a sharp point that is more spreading than the tip itself, and that persists on the fruit.

Leaves and stems: Leaf attachment: opposite Leaf type: simple

[photo of leaves] Leaves are simple and opposite, the pairs set at right angles to the ones above and below, the lowest leaves more oblong elliptic becoming lance linear up the stem, ¾ to 3 inches long, ¼ to about ½ inch wide, pointed or blunt at the tip, toothless and hairless, mostly green or tinged red. The leaf base is typically narrowly to broadly lobed, somewhat clasping the stem, but is sometimes merely heart shaped. Stems are mostly erect, smooth, green to bright red, mostly branched in the lower plant and more sparsely above, the branches ascending.

Fruit: Fruit type: capsule/pod

[photo of fruit] Fruit is a round capsule ¼ inch or less in diameter, with 4 chambers, turning red as the seed ripens.

Notes:

Valley Redstem inhabits the muddy banks and mudflats of the Red River and its tributaries as well as the entire reach of the Minnesota River. Mostly terrestrial and appearing after seasonal high waters have receded, it will persist in standing water if water levels rise again. While not found in the same habitat, it may perhaps be confused with either Toothcup (Rotala ramosior) or Water Purslane (Ludwigia palustris), especially when petals are absent. In Rotala, the flowers are always single in the axils, the leaves tapering to a short stalk. Ludwigia is always creeping, rooting at the nodes, and also has only single flowers in the axils with more broadly oval leaves on a longer tapered stalk.

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More photos

Photos courtesy Peter M. Dziuk taken at Louisville Swamp, Scott County.

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