Heteranthera dubia (Jacq.) MacMill.
Water Star Grass
Family - Pontederiaceae
Stems - Elongate, usually submerged.
Stem and node.
Leaves - Alternate, to 15 cm, 2-5 mm wide, linear, tapered to sessile base.
Inflorescence - Flowers solitary and sessile in leaf axils.
Flowers - Perianth of 6 tepals, yellow, actinomorphic, with elongate tube to 7 cm long, lobes linear, to 12 mm. Stamens 3, all same length. Ovary superior, with 3 locules. Style 1.
Flowering - June - September.
Habitat - Streams, springs and spring branches, sloughs.
Origin - Native to U.S.
Other info. - This little species grows in scattered areas mostly in the southern half of the state, always in very wet places (mud to shallow water). It is an easy plant to identify because of its long, linear leaves, solitary yellow flowers, and habitat. There are five species of Heteranthera in Missouri. Like many plants whose common name contains the word "grass," this one is unrelated to the grasses.
Photographs taken along the shores of the Current River, Shannon County, MO., 8-2-03 (DETenaglia), also at Busch Wildlife Area, St. Charles County, MO, 7-29-2015 (SRTurner).