Ammannia coccinea

Native

Wet. Riverbanks, lake shores, roadside ditches, sloughs, swales, inland floodplane forests. Full sun.

July to October

Rose-purple

1′ to 2′

This plant is an annual rising from a shallow tuft of roots.

The stems are erect to a height of about 1′ to 2′ or bend down near the base and lie on the ground. They are 4-angled, branched and hairless.

The leaves are opposite, stalkless, untoothed, up to 3″ long, straight, and narrow, with more or less parallel sides. They narrow at the tip and widen at the base to nearly ear-like lobes that clasp the stem. They have a prominent central vein. They are green, sometimes tinted with red.

The inflorescence is a tight cluster of 3 to 5 flowers rising from the leaf axils.

The flowers are borne on short flower stalks, are about ¼″ wide, and have 4 or 5 small rose-purple petals.

The fruit is a rounded capsule a little over ⅛″ in diameter containing many tiny seeds.

Robust toothcup (Ammannia robusta) has light pink flowers and 1 to 3 flowers per leaf axil. It does not occur in Minnesota.

Lowland rotala (Rotala ramosior) has white flowers and only a single flower per leaf axil. The leaves attach to the stem without a stalk but do not clasp the stem.