Arnoglossum atriplicifolium (L.) H. Rob.

Pale Indian Plantain

Arnoglossum atriplicifolium plant

Family - Asteraceae

Stems - To +2m tall, glabrous, glaucous, herbaceous, erect, from a short caudex and large thickened roots, fistulose, simple but widely branching in the inflorescence, sometimes with few black glands near nodes (from leaf petioles).

Arnoglossum atriplicifolium stemGlaucous stem

Leaves - Basal leaves long-petiolate. Petioles with an adaxial groove (groove "U" shaped), often purplish at the base. Blades large, cordate, coarse shallow dentate, deep green adaxially, glaucous abaxially, to +20cm long, +15cm broad. Sinuses and teeth rounded. Cauline leaves similar to basals but reduced, becoming more sharply toothed, 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 corymbiform arrangement of multiple flower heads, to +/-20cm broad at maturity. The peduncles glabrous. Some divisions of the inflorescence subtended by small bracts.

Involucre - Uniseriate, of linear bracts (5-6), to 1cm tall, 3-4mm in diameter, cylindric. Phyllaries overlapping on margins, appearing united, with scarious margins, yellowish-green to greenish-white, subacute at apex, to 1.5mm broad.

Arnoglossum atriplicifolium involucreInvolucre.

Ray flowers - Absent.

Disk flowers - 4-5 per flower head, exserted from the involucre. Corolla greenish-white, glabrous, 5-lobed. Corolla tube to 5mm long. Lobes to +3mm long, linear, curling. Stamens 5, adnate at the apex of the corolla tube, exserted. Filaments green, glabrous, 2mm long. Anthers connate around the style, brownish, to +2mm long. Style green, glabrous, well exserted, bifurcate. Stigmas spreading. Achenes green in flower, +/-2mm long, terete, glabrous. Pappus of white barbellate bristles, to 5mm long, many.

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. - The leaves of this species are quite thick and leathery. The plant is often found wilted in periods of little rain. The leaf pictured above is typical of the plants I have encountered but the leaves can be quite variable in shape.

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).