Arnoglossum is a small genus of flowering plants in the family Asteraceae (tribe Senecioneae), comprising eight species native to eastern North America, ranging from Ontario south through the eastern and central United States. Commonly known as Indian plantains, the plants take their vernacular name from a superficial resemblance of their broad, often basal leaves to those of the unrelated common plantain (Plantago spp.) — the two groups are not closely related.
The genus was formally described in 1817. Its taxonomic history is complicated: many species now placed in Arnoglossum were previously assigned to Cacalia, Mesadenia, or Senecio, and the broader tribe Senecioneae has undergone extensive revision in recent decades. The reclassification by Harold Robinson in the 1970s–1980s consolidated most North American "cacalias" into Arnoglossum on the basis of morphological and molecular distinctions.
Plants in the genus are typically upright herbaceous perennials bearing alternate, petiolate leaves that vary considerably in shape — from kidney-shaped to ovate to somewhat triangular — giving rise to epithets such as diversifolium (variable-leaved) and reniforme (kidney-shaped). The flower heads are small, discoid (lacking ray florets), and clustered in flat-topped corymbs; florets are white to creamy. Most species favour moist to mesic habitats such as bottomland forests, floodplains, and open woodlands of the eastern United States.
Notable members include Arnoglossum atriplicifolium (pale Indian plantain), one of the most widespread species in eastern and central North America, and Arnoglossum plantagineum (tuberous Indian plantain), which extends as far north as Ontario. Several species — including A. floridanum and A. sulcatum — have restricted ranges in the southeastern United States and are of conservation concern.
Etymology
The name Arnoglossum derives from the Greek words arnos (lamb) and glossum (tongue) — literally "lamb's tongue" — which was the ancient Greek name applied to certain species of Plantago. The common name "Indian plantain" similarly references the plantain-like leaves, though Arnoglossum is not related to Plantago.
Distribution
All species in the genus are native to eastern North America. The range extends from southern Ontario in Canada southward through the eastern and central United States, with several species restricted to Florida, Georgia, Alabama, and Mississippi. Arnoglossum plantagineum has the broadest range, reaching from Ontario south to Texas and Alabama; A. atriplicifolium is widespread across much of the eastern and central United States.
Taxonomy Notes
Arnoglossum belongs to the tribe Senecioneae within Asteraceae and has experienced considerable taxonomic revision. Many of its species were formerly placed in Cacalia, Mesadenia, or Senecio before being transferred to the current genus. The tribe Senecioneae as a whole continues to be subject to revision. The family name Compositae is a synonym for Asteraceae.
