Diarrhena obovata
Beak grass
Image of Diarrhena obovata

Photo by Bradford S. Slaughter 

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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

  • State Status: T
  • State Rank: S2
  • Global Rank: G4G5


County NameNumber of OccurrencesYear Last Observed
St. Clair12011
Distribution map for Diarrhena obovata

Updated 5/15/2018. 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.


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.

General Survey Guidelines

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

Survey Methods

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Sep 24, 2018]

More Information

See MNFI Species Abstract


Survey References

Technical References

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