Acalypha rhomboidea Raf.

Three-Seeded Mercury

Acalypha rhomboidea plant

Family - Euphorbiaceae

Habit - Taprooted, monoecious, annual forb.

Stems - Herbaceous, erect, branching, to +/-50cm tall, antrorse pubescent, single from the base. Sap clear.

Acalypha rhomboidea stem

Leaves - Alternate, petiolate. Petioles to +/-4cm long, antrorse pubescent. Blades lanceolate-rhombic to rhombic, crenate-serrate, deep green and sparse antrorse strigose above(with a somewhat shiny appearance), light green and mostly glabrous below(or with a few very sparse hairs on the veins), acute. to +/-7cm long, +/-4cm broad. Lowest pair of lateral veins coming from the base of the blade.

Acalypha rhomboidea leaves

Inflorescence - Axillary bracteate androgynous racemes to 2cm long. Bracts subtending the female flowers serrate, to 1.3cm long, 1.5cm broad, mostly glabrous above, sparse pubescent and glandular below. Teeth of bracts to 5mm long, acute. Margins of teeth antrorse strigillose and glandular pubescent. Peduncle of male flowers densely antrorse pubescent. Pedicels of male flowers to .3mm long.

Acalypha rhomboidea inflorescencesAxillary inflorescences.

Acalypha rhomboidea bractsStaminate inflorescences with subtending bracts.

Flowers - Male flowers in capitate clusters terminating the peduncle. Flowers minute. Sepals 4, golden-green, antrorsely bent, .3mm long, acute to blunt. Stamens many. Female flowers apetalous, the sepals minute and green. Ovary 3-locular, pubescent. Styles 3, laciniate.

Acalypha rhomboidea flowersStaminate flowers close-up.

Fruits - Fruits 3-locular, 3-seeded. Mature capsule to +/-2mm in diameter, pubescent at the apex.

Acalypha rhomboidea fruit3-Locular fruit.

Flowering - July - October.

Habitat - Open woods, moist soils, gravel bars, waste ground, roadsides, railroads.

Origin - Native to U.S.

Other info. - This species is found throughout Missouri. The plant is a member of the Euphorbiaceae but unlike many members of that family, it has clear sap. The typical plants from this family have milky white sap. This species can grow larger than the other members of this genus in Missouri. It is distinguished from siblings of similar appearance by having very long leaf petioles (often as long as the leaf blades) and three-lobed (three-locular) fruits.

Photographs taken in the Ozark Scenic Riverways, Shannon County, MO., 8-2-03 (DETenaglia); also at Pacific Palisades Conservation Area, MO, 9-22-2012, and Catawissa Conservation Area, Franklin County, MO, 9-11-2018 (SRTurner).