Plants and Animals

Diarrhena obovata Beak grass

Key Characteristics

A dense, clump-forming perennial forb of floodplain forests, often within close proximity to riverbanks; relatively broad, 1-2 cm wide, shiny leaves with a prominent off-set mid-vein; inflorescence consisting of a long, drooping terminal panicle with well-spaced, very short, beaked spikelets that expand to become shiny and egg-shaped at maturity.

Status and Rank

US Status: No Status/Not Listed
State Status: T - Threatened (legally protected)
Global Rank: G4G5 - Rank is uncertain, ranging from apparently secure to secure
State Rank: S2 - Imperiled


CountyNumber of OccurrencesYear Last Observed
Allegan 1 2018
Barry 2 2019
Berrien 1 2015
Clinton 1 2003
Ingham 5 2013
Ionia 2 2015
Kalamazoo 1 2007
Kent 3 2016
Lapeer 1 2003
Lenawee 6 2018
Midland 6 2016
Monroe 1 1988
Ottawa 1 2014
Saginaw 2 2016
St. Clair 1 2011
Tuscola 1 2003
Wayne 4 2003

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


In Michigan and throughout its range American beak grass is almost exclusively found in lowland riparian forests.

Natural Community Types

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Associated Plants

Overstory species include silver maple, black maple, red ash, Eastern sycamore, Eastern cottonwood, and black willow; common understory shrubs include spicebush and bladdernut; typical groundcover plants consist of green dragon, Jack-in-the-pulpit, wild ginger, mermaid weed, wild geranium, wood nettle, clearweed, cut-leaved coneflower, tall meadow-rue, wingstem, creamy white violet, and Canada violet.  Rare associates may include such species as green violet, goldenseal, red mulberry, ginseng, pumpkin ash, cup-plant, snow trillium, wahoo, and twinleaf, among several other taxa known to occur in southern floodplain forests.

Management Recommendations

The most severe threats to this species are excessive alteration of habitat and competition from agressive non-native plants. The best management strategies for conserving American beak grass include removing invasive species, protecting the hydrological and cyclical flooding regime of riparian systems, and maintaining healthy, intact, mature floodplain forests in contiguous corridors wherever possible.

Survey Methods

Random meander search covers areas that appear likely to have rare taxa, based on habitat and the judgment of the investigator.

  • Meander search

    • Survey Period: From third week of August to fourth week of September


Survey References

  • Elzinga, C.L., D.W. Salzer, and J.W. Willoughby. 1998. Measuring and Monitoring Plant Populations. The Nature Conservancy and Bureau of Land Management, Denver. BLM Technical Reference 1730-1. 477pp.
  • Nelson, J.R. 1984. Rare Plant Field Survey Guidelines. In: J.P. Smith and R. York. Inventory of rare and endangered vascular plants of California. 3rd Ed. California Native Plant Society, Berkeley. 174pp.
  • Nelson, J.R. 1986. Rare Plant Surveys: Techniques For Impact Assessment. Natural Areas Journal 5(3):18-30.
  • Nelson, J.R. 1987. Rare Plant Surveys: Techniques for Impact Assessment. In: Conservation and management of rare and endangered plants. Ed. T.S. Elias. California Native Plant Society, Sacramento. 8pp.

Technical References

  • Fernald, M.L. 1950. Gray's Manual of Botany; eighth edition, illustrated. D. Van Nostrand Company. lxiv + 1632 pp.
  • Flora of North America Editorial Committee. 2007. Flora of North America, North of Mexico. Volume 24: Magnoliaphyta: Commelinidae (in part): Poaceae, part 1. Oxford University Press, New York. 910pp.
  • Gleason, H. A., and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. Second edition. The New York Botanical Garden, Bronx. 910pp.
  • Godfrey, R.K. and Wooten. 1979. Aquatic and Wetland Plants of Southeastern United States. Monocotyledons. University of Georgia Press, Athens. 933pp.
  • Hitchcock, A. S. 1951. Manual of the Grasses of the United States. Second ed. Revised by A. Chase. U.S. Department of Agriculture Miscellaneous Publications 200. 1051pp.
  • Holmgren, N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the vascular plants of Northeastern United States and adjacent Canada. New York Botanical Garden, Bronx. 937pp.
  • Swink, F. and G. Wilhelm. 1994. Plants of the Chicago Region, 4th ed. Indiana Academy of Science, Indianapolis. 921pp.