Alisma triviale Pursh

Northern Water Plantain

Alisma triviale plant

Family - Alismataceae

Habit - Rhizomatous, perennial, emergent aquatic forb.

Stems - Absent except for inflorescence stalk.

Alisma triviale rosetteBasal rosette.

Leaves - Basal, petiolate. Petioles stout, with spongy tissue internally. Blades to 20 cm long, broadly elliptic to ovate, simple, entire, glabrous. Venation with 1-3 pairs of main veins arcing from near the base of the midrib and rejoining near the apex, these connected by finer, angled veins running parallel to one another.

Alisma triviale petiolePetiole cross section.

Alisma triviale leaves

Alisma triviale leaf2Leaf lower surface.

Inflorescence - Erect panicles with whorled branches. Branch nodes with narrowly triangular leaflike bracts.

Alisma triviale nodeInflorescence node.

Flowers - Actinomorphic, 3-merous, perfect, subtended by bracts. Sepals ovate, persistent, green, often with hyaline margins. Petals to 3 mm long, significantly longer than sepals, white. Stamens 6, the filaments as long as or longer than the anthers. Pistils 10-28, in a single ring on the flat receptacle. Styles lateral.

Alisma triviale sepalsSepals.

Alisma triviale flowerFlowers.

Alisma triviale flower3

Alisma triviale flower2Flower and fruits.

Alisma triviale fruitRing of fruits.

Fruits - Fruits 15-24, 1.8-3.0 mm long, borne in a ring 3.5-4.5 mm in diameter, the back with 1 dorsal groove.

Flowering - May - September.

Habitat - Pond margins, creeks, sloughs, marshes, ditches, in mud.

Origin - Native to U.S.

Other info. - This aquatic species is found scattered throughout most of the state and across most of the northern and western U.S. It has larger flowers and fruit rings than the somewhat more common A. subcordatum, with flower petals which clearly exceed the sepals. "Larger" in this context is a distinctly relative term - the flowers are still quite small and inconspicuous. A well-developed inflorescence can have many dozens of flowers within a lacy network of wiry branches. The plant is typically found in open areas of mud which has been exposed by slowly receding water levels.

Plants of this genus are a food source for aquatic wildlife such as muskrats. The rhizomes are eaten as well as the leaves. The starchy rootstocks have been cooked in the fall for human consumption.

Photographs taken off Hwy H., Shannon County, MO., 7-18-03 and 6-25-04 (DETenaglia); also along the Katy Trail near Dutzow, Warren County, MO, 9-15-2017, and Marais Temps Clair Conservation Area, St. Charles County, MO, 7-22-2013 (SRTurner).


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