Echinodorus cordifolius (L.) Griseb.
Family - Alismataceae
Stems - Absent.
Leaf - Basal, with long petioles. Leaf blades broadly ovate with cordate bases. Venation with palmate main veins arching from the base of the midrib and rejoining near the apex, these connected by a series of parallel, angled veins.
Inflorescence - Arching, prostrate at maturity, the nodes sometimes rooting and producing plantlets from bulbils, with several to many whorls of 5-15 flowers, unbranched. Inflorescence bracts 3, 10-25 mm long, linear-lanceolate, acuminate. Additional smaller bractlets also present.
Bracts and sepals.
Flowers - Flowers perfect. Sepals 5-7 mm long, ovate to orbicular, persistent, reflexed in fruit. Petals 6-12 mm long, white, obovate. Stamens many, the anthers 1.0-1.5 mm long, the filament attached toward the middle of the anther. Pistils many, forming a dense headlike cluster on the expanded receptacle.
Fruits - Borne in orbicular clusters. Fruits 1.8-2.5 mm long, brown, with 6-8 curved ribs, the beak 0.2-0.5 mm long, attached obliquely.
Immature fruit clusters.
Flowering - July - September.
Habitat - Emergent aquatics in mud along margins of ponds, sloughs, swamps, marshes, ditches, often in shallow water.
Origin - Native to the U.S.
Other info. - This plant is widely scattered, and not all that common in the state except in the Bootheel region. It is easily recognized by its aquatic habitat, interesting leaves, and arching or prostrate inflorescences. It is unique among the Missouri Alismataceae family members in having nodes with several flowers all pointing in the same direction. There is some evidence that this species may hybridize with the closely related E. berteroi.
Photographs taken at Otter Slough Conservation Area, Stoddard County, MO, 7-31-2015 (SRTurner).