Arnoglossum reniforme (Hook.) H. Rob.

Great Indian Plantain

Arnoglossum reniforme plant

Family - Asteraceae

Stems - Single or multiple from base, erect, herbaceous but stout, mostly simple, to 1.5m tall, hollow, angled, ribbed, with vertical striations, glabrous, reddish-purple at the base.

Arnoglossum reniforme stem

Leaves - Alternate, petiolate. Petioles longest at the base of the plant, reduced upward, to +/-18cm long, glabrous, with a shallow adaxial groove. Groove reddish on the margins. Blades typically reniform in the lower 2/3 of the plant, becoming truncate at the base in the apical 1/3 of the plant, to +/-20cm broad, +/-15cm long, coarse and irregular dentate, green above, silvery-green below, with impressed veins above, expressed veins below, pubescent with multicellular trichomes (more so below), with a rubbery texture.

Arnoglossum reniforme leafAdaxial surface of leaves.

Arnoglossum reniforme leafAbaxial surface of leaves.

Inflorescence - Terminal corymbiform arrangement of flower heads. Peduncles whitened, glabrous. Each division of the inflorescence subtended by a minute bract. Bracts subulate, white, 1-5mm long.

Arnoglossum reniforme inflorescenceInflorescence

Involucre -Cylindric, whitened, to 1cm tall, glabrous. Phyllaries 5, united, with a rounded keel that gives the involucre a carinate look, glabrous.

Ray flowers - Absent.

Disk flowers - Flowers typically 5 per flower head. Apices of flowers exceeding the involucre, otherwise enclosed in it. Corolla tube glabrous, greenish, 7mm long, 5-lobed, expanded at the apex into a short campanulate tube. The tube to 1mm long. Lobes white, glabrous, curled, to 3mm long (uncurled), -1mm broad, acute. Stamens 5, adnate at the base of the campanulate portion of the corolla tube. Filaments filiform, yellowish-tan, glabrous. Anthers tan-brown, +2mm long, connate around the style, exserted. Style exserted beyond the anthers, glabrous, white, bifurcate. The free ends of the style recurved all the way back to the main body of the style. Pappus of white capillary bristles to 7mm long. Achene green and glabrous in flower, cylindric, to 3mm long.

Arnoglossum reniforme flowersFlower heads.

Arnoglossum reniforme inflorescenceFlorets

Flowering - May - September.

Habitat - Rich woods, north or east-facing slopes, ravines, bluffs along streams.

Origin - Native to U.S.

Other info. - This striking species can be found in the mainly in the eastern half of the state as well as a few extreme southwestern counties. The plant is very easy to ID in the field because of its distinct basal leaves. The plant is most often seen as just basals because it takes about 2-3 years to bloom for the first time. It grows well from seed and would make a fine plant in cultivation.

Photographs taken at Alley Spring, Shannon County, MO., 6-27-03 (DETenaglia); also at Shaw Nature Reserve, Franklin County, MO, 6-27-2008, and in Weldon Spring Conservation Area, St. Charles County, MO, 6-19-2009 (SRTurner).