Arnoglossum atriplicifolium (L.) H. Rob.

Pale Indian Plantain

Arnoglossum atriplicifolium plant

Family - Asteraceae

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

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

Arnoglossum atriplicifolium stemGlaucous stem

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 leaf

Arnoglossum atriplicifolium leafGlaucous leaf underside

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

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 involucreInvolucre.

Ray flowers - Absent.

Disk flowers - 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 flowersFlowers.

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

Arnoglossum atriplicifolium fruitsFruits.

Flowering - June - October.

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

Origin - Native to U.S.

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 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).


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