Scientific name

Hemianthus Nutt.

Common names

baby’s tears, Nuttall's mud-flower, pearl grass



Could be confused with

Elatine, Elodea, Hydrilla, Micranthemum, Rotala, Tonina

Native distribution

North and Central America, Caribbean

Species commonly cultivated

Hemianthus callitrichoides Griseb. (Micranthemum umbrosum (J.F. Gmel.) Blake (southeastern North America, South America)

H. micranthemoides Nutt. (eastern North America) (Micranthemum micranthemoides)

Adventive distribution


Weed status

not weedy


small, emergent, and amphibious creeping stem plant

Brief description

Annual or perennial. Amphibious. Stem creeping or ascending, rooted at nodes. Leaves opposite, decussate or in whorls of 3-4, sessile; leaf blade orbicular, obovate to ovate, venation indistinct; margin entire. Flowers minute, solitary, zygomorphic, short-pedicellate; sepals fused, lobes 4; corolla tube 1-lipped, abaxial lip 3-lobed; stamens 2-4. Dispersal by stem fragments or seed.

Natural habitat

bright sunlight, lakes, rivers, and streams; shallow water and muddy littoral zone

Additional comments

Hemianthus is considered by some authorities as a synonym of Micranthemum, and Hemianthus is sometimes used in the aquarium trade. A fundamental difference between Hemianthus and Micranthemum is the corolla tube lobes; Hemianthus has a one-lipped corolla tube with adaxial lobes absent and a three lobed abaxial lip, while Micranthemum has a two-lipped corolla tube with 3 adaxial lobes and two abaxial lobes united, appearing as one lobe.