Arnoglossum atriplicifolium (L.) H. Rob.

Pale Indian Plantain


CC = 4
CW = 5
MOC = 49

© DETenaglia

Family - Asteraceae/Senecioneae

Habit - Perennial forb from a short caudex and fleshy roots.

Stems - Erect, to 3 m, round in cross section, simple but widely branching in the inflorescence, sometimes with few black glands near nodes (from leaf petioles), glabrous, glaucous.

Arnoglossum_atriplicifolium_stem.jpg Glaucous stem

© DETenaglia

Leaves - Basal and alternate, petiolate, progressively reduced in size upward, glabrous, glaucous. Petioles with an adaxial groove, often purplish at the base. Blades to 45 cm, broadly triangular-ovate, often shallowly palmately lobed, coarsely toothed, cordate, deep green adaxially, pale and glaucous abaxially. Sinuses and teeth rounded, becoming more sharply toothed upward on plant, often cuneate at the base of the blade or truncate. Petioles of cauline leaves often with abaxial black glands.

Arnoglossum_atriplicifolium_leaf1.jpg Leaf, adaxial.

© DETenaglia

Arnoglossum_atriplicifolium_leaf2.jpg Glaucous leaf underside

© SRTurner

Arnoglossum_atriplicifolium_leaf.jpg Pressed leaf.

© DETenaglia

Inflorescence - Terminal and axillary panicles, usually flat-topped, the peduncles glabrous. Some inflorescence branches subtended by small bracts.

Arnoglossum_atriplicifolium_inflorescence.jpg Inflorescence.

© DETenaglia

Arnoglossum_atriplicifolium_inflorescence2.jpg Inflorescence portion.

© DETenaglia

Heads - Discoid, cylindrical, glabrous. Involucre 7-9 mm long, the 5 inner bracts rounded dorsally, with margins overlapping, greenish white, outer series usually absent.

Arnoglossum_atriplicifolium_flowers.jpg Involucre.

© DETenaglia

Flowers - Ray florets absent. Disk florets 4-5 per flower head, 8-10 mm long, exserted from the involucre. Corolla greenish-white, glabrous, 5-lobed. Corolla lobes to 3 mm long, linear, curling. Stamens 5, adnate at the apex of the corolla tube, exserted. Filaments green, glabrous, 2 mm long. Anthers connate around the style, brownish, to 2 mm long. Style green, glabrous, exserted. Stigmas spreading. Pappus of white barbellate bristles, to 5 mm long.

Arnoglossum_atriplicifolium_flowers3.jpg Flowers.

© SRTurner

Fruits - Achenes 3-5 mm long, terete, glabrous, ribbed, beakless.

Arnoglossum_atriplicifolium_fruits.jpg Fruits.

© SRTurner

Flowering - June - October.

Habitat - Wooded slopes, rocky stream margins, open woods, railroads, roadsides.

Origin - Native to the U.S.

Lookalikes - A. reniforme, A. plantagineum.

Other info. - This species is found scattered throughout most of Missouri, and its U.S. range includes most of the eastern half of the country. The species is easy to identify. It could be confused with its sibling, A. reniforme, but the leaf undersides of that species are green and not conspicuously glaucous. The leaves of A. atriplicifolium also tend to be more angular in shape, and are also thick and leathery, in addition to having the signature pale undersides. They often droop during dry spells. The leaves pictured above are typical but the leaves can be quite variable in shape.

When fully in flower, the plants are majestic. The species is deserving of wider cultivation, though it is currently not widely available.

The species was long known as Cacalia atriplicifolia.

Photographs taken at Taum Sauk Mountain, MO., 7-28-03 (DETenaglia); also at Holly Ridge Conservation Area, Stoddard County, MO, 8-22-2009, Weldon Spring Conservation Area, St. Charles County, MO, 8-16-2011, Cuivre River State Park, Lincoln County, MO, 7-15-2013, Young Conservation Area, Jefferson County, MO, 10-8-2015, and Glassberg Conservation Area, Jefferson County, MO, 8-7-2016 (SRTurner).