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Ovate Beak Grass (Diarrhena obovata)

Life history

Species overview

Ovate Beak Grass (Diarrhena obovata), a Wisconsin Endangered plant, is found in moist streamside deciduous forests. Blooming occurs early August through early September; fruiting occurs early September through early October. The optimal identification period for this species is early August through early October.

Synonyms: Diarrhena americana, Diarrhena americana var. obovata


  • Distinguishing characteristics: Cespitose with mostly basal leaves; leaf with an off-center midvein, sheaths pubsecent; inflorescence long, drooping; spikelets flattened, spreading, few-flowered; grains large. Glumes and lemmas shorter than in D. americana var. americana.
  • Flower characteristics: Inflorescence 10 to 30 cm long, drooping; spikelets flattened by the spreading of the lemmas, 3- to 5-flowered; panicle scabrous, long and slender, few-flowered.
  • Fruit characteristics: First glume triangular, 1.9 to 2.8 mm; second glume oblong, cuspidate, 2.4 to 4.3 mm; lemmas 5.2 to 6.8 mm, abruptly rounded into a short cusp, smooth; callus glabrous; grain large.
  • Leaf characteristics: Sheaths pubescent toward the top; blades 20 to 40 cm long, 10 to 18 mm wide, with midvein off-center.


  • Blooming phenology: early August through early September
  • Fruiting phenology: early September through early October
  • Optimum time to identify: The optimal identification period for this species is early August through early October


  • Growth form: Graminoid
  • Vegetative reproduction: Rhizomatous and densely clonal
  • Life cycle: Perennial
  • Comments: Associated Species: Fraxinus pennsylvanica, Ulmus americana, Acer saccharinum, Quecus bicolor, Celtis occidentalis.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - state and federal - and the rank (S and G Ranks) for Ovate Beak Grass (Diarrhena obovata). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Documented locations of Diarrhena obovata in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusEND
Federal Status in Wisconsinnone
State RankS2
Global RankG4G5
Tracked by NHIY

Habitats and landscapes

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

General habitat information

  • Habitat description: Found in moist streamside deciduous forests.
  • Soils: Moist soils.

Natural communities

This table lists the natural communities that are associated with Ovate Beak Grass. Scores for natural community associations are: "significant" association (score=3), "moderate association" (score=2) or the species can be present but is only weakly associated with the community (score=1).

Natural communities score
Floodplain Forest 3
Southern Mesic Forest 2

Ecological landscapes

This table lists the ecological landscape association scores for Ovate Beak Grass. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

Species guidance

The Endangered Resources Program has developed avoidance measures and management guidelines for plants on the Natural Heritage Working List. These are a work in progress, and we welcome your suggestions and feedback. Sources used in developing this information can be found here.

Avoidance measures

These are specific actions designed to avoid "take" (mortality) of this species.

  • Avoid known individual plant locations and conduct operations elsewhere when they are least likely to cause damage. Ideally, this would involve frozen, snow-covered ground. However, in areas of the state where frozen conditions are unreliable, very dry soils late in the growing season might be the best available alternative. Consult with a biologist, if needed.
  • Avoid broadcast spraying of herbicides; use care with spot spraying.

Management guidance

Management guidelines are additional considerations that may help maintain or enhance habitat for this species

  • Follow BMPs, especially around streams and use care near ravines, steep slopes, cliffs, rock outcrops, etc.
  • Maintain high forest canopy cover; this species requires shaded habitat conditions.
  • Minimize disturbance to hydrology, including soil disturbance from rutting.


Ovate Beak Grass Photo.

Photo © Emmet Judziewicz.

Ovate Beak Grass Photo.

The fruit of Diarrhena obovata is a large, inflated caryopsis (grain).

Photo by Ryan O'Connor, Wisconsin DNR.

Ovate Beak Grass Photo.

Diarrhena obovata is a clump-forming grass of floodplains and moist forests.

Photo by Ryan O'Connor, Wisconsin DNR.

Ovate Beak Grass Photo.

Photo © John Zaborsky.

Ovate Beak Grass Photo.

Photo © John Zaborsky.

Support for Wisconsin's rare plant information has been provided by the Division of Forestry, the Endangered Resources Fund and the Wisconsin Rare Plant Preservation Fund. To donate, visit the Natural Resources Foundation of Wisconsin [exit DNR].

Last revised: Wednesday, May 05, 2021
Southwest Savanna Southern Lake Michigan Coastal Western Coulees and Ridges Southeast Glacial Plains Central Sand Hills Central Lake Michigan Coastal Central Sand Plains Northern Lake Michigan Coastal Northern Lake Michigan Coastal Northeast Sands Western Prairie North Central Forest Northern Highlands Northwest Lowlands Northwest Sands Northwest Lowlands Superior Coastal Plains Forest Transition