Rare Species Guide

  Synonyms

Conophora reniformis, Cacalia muehlenbergii, Cacalia muhlenbergii, Arnoglossum muehlenbergii, Mesadenia reniformis, Senecio atriplicifolius var. reniformis, Senecio reniformis

  Basis for Listing

Arnoglossum reniforme (great Indian plantain) is a long-lived perennial forb, which reaches the northwestern edge of its range in southeastern Minnesota. Examination of herbaria collections indicates this species has always had a limited range in the state. Despite comprehensive botanical surveys having been conducted throughout the species’ range since the mid-1980s, only a few additional populations have been found. Furthermore, the majority of the species’ known populations consist of less than 100 individuals. As this plant is large and quite distinctive, it is unlikely that it would have been overlooked.

Arnoglossum reniforme is typically associated with floodplain forest communities on alluvial terraces along smaller streams. Since settlement times, large expanses of floodplain forests in southern Minnesota have been lost due to conversion to agriculture, urbanization, and the damming and channelization of rivers. Given the species' limited geographic range, the small number of documented populations, and the small size of those populations, the historic loss and degradation of floodplain forest habitat, and potential loss of additional habitat due to competing land use practices, Arnoglossum reniforme was listed as a threatened species in 2013.

  Description

Arnoglossum reniforme is a tall and robust perennial forb, which reaches a height of 1-3 m (3-10 ft.). Plants are often observed with multiple stems arising from the same root-crown. The stem is ridged to angulate and usually glabrous. The plant has large basal leaves, often the size of a dinner plate; the petioles are up to 30 cm (12 in.) long; blades are reniform or ovate-cordate and >40 cm (>16 in.) long, with 3-5 main veins and lobed or dentate margins. Cauline leaves are proximal and petiolate, with margins entire, serrate, or dentate. Leaves are green on both sides. The inflorescence is a flat-topped umbel, with numerous heads. The flowers are white to cream or greenish and cylindrical in shape.  

This species is similar in appearance to A. atriplicifolium (pale Indian plantain), which is not known to occur in Minnesota, though it has been documented in Iowa and Wisconsin. Arnoglossum atriplicifolium can be distinguished from A. reniforme by its mostly smooth stems and by its pale and glaucous lower leaf surfaces.

  Habitat

In Minnesota, most populations of A. reniforme are located along stream banks, terrace forests, and floodplain forests of small to medium sized rivers in the southeastern portion of the state (Paleozoic Plateau Section). Rarely, plants have been observed in wet prairie or wet meadow communities adjacent to these same rivers and streams. The species tends to be found in direct sun along stream banks or in partial shade in forests with interrupted to patchy canopy cover. Plants typically occur in settings that experience infrequent or short duration flooding, such as those that occur during snow pack melting or major flood events. Across its North American range, it appears more often in woodland settings. Some of its more commonly encountered associates in Minnesota include: Rudbeckia laciniata var. laciniata (tall coneflower), Angelica atropurpurea (angelica), Laportea canadensis (wood nettle), Silphium perfoliatum var. perfoliatum (cup plant), Cryptotaenia canadensis (honewort), Napaea dioica (glade mallow), and Solidago gigantea (giant goldenrod).

  Biology / Life History

Arnoglossum reniforme is a perennial, with fibrous roots. It can be found blooming from mid-June through late July and in fruit from mid-July through late August. Robertson (1928) observed a variety of pollinators visiting the flowers of A. reniforme, including bees and wasps of several different taxonomic families.

  Conservation / Management

Arnoglossum reniforme is rare in the state due to its restricted range and limited habitat. As with most populations located along streams and rivers, it is not clear how changes in up-stream land-use practices or changes in stream flow could potentially impact populations of this species. A potential threat to populations could occur with the removal of canopy species and the subsequent establishment of Phalaris arundinacea (reed canary grass). The species has also been observed in grazed bottomland forests and appears tolerant of light grazing by cattle. At one site in Mower County, the species has flourished, and the population has expanded extensively along a small stream where the landowner has been removing a dense understory of Rhamnus cathartica (common buckthorn).

  Best Time to Search

The best time to search for this large and conspicuous species is from early June through late September.  

  Conservation Efforts in Minnesota

Most known sites are located on private land, and there has not been any land acquisition done by conservation groups or agencies specifically for this species in Minnesota.

  Authors/Revisions

Derek S. Anderson (MNDNR), 2018

(Note: all content ©MNDNR)

  References and Additional Information

Anderson, L. C. 2006. Arnoglossum. Pages 622-625 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 20. Oxford University Press, New York, New York.

Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the eastern broadleaf forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 394 pp.

Minnesota Department of Natural Resources. 2006. Tomorrow's habitat for the wild and rare: An action plan for Minnesota wildlife, comprehensive wildlife conservation strategy. Division of Ecological Services, Minnesota Department of Natural Resources. 297 pp. + appendices.

NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia.

Robertson, C. 1928. Flowers and insects: lists of visitors of four hundred and fifty-three flowers. n.p. Carlinville, Illinois. 236 pp.