Heteranthera dubia (Jacq.) MacMill.
CC = 7
CW = -5
MOC = 32
Family - Pontederiaceae
Habit - Perennial, emergent aquatic forb, sometimes stranded on mud.
Stems - Elongate, usually submerged.
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.
Fruit - Slender, thin-walled capsules to 2 cm long. Seeds 7-30, 0.5-1.5 mm long, with 8-22 longitudinal ribs.
Flowering - June - September.
Habitat - Streams, springs and spring branches, sloughs.
Origin - Native to the 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 occurs widely scattered throughout much of the continental U.S. It is an easy plant to identify due to its long, linear leaves, solitary yellow flowers, and wet 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. Some members of this genus have stamens of different lengths within each flower, a trait responsible for the Heteranthera genus name. Some botanists segregate H. dubia into its own genus, Zosterella.
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, and Onondaga Cave State Park, Crawford County, MO, 7-24-2018 (SRTurner).