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Flattened Oatgrass (Danthonia compressa)

Life history

Species overview

Flattened Oatgrass (Danthonia compressa), a plant, is found in dry hardwood forests and meadows. Blooming occurs April to May; fruiting occurs early to late summer. The optimal identification period for this species is late spring.

Synonyms: Danthonia allenii


  • Distinguishing characteristics: Most likely to be confused with Danthonia spicata, which has having shorter teeth on the lemmas (0.8 to 1.8 mm), and white tufts of hairs on the sheaths.
  • Flower characteristics: Inflorescences are pale green and on lax pedicels, which are 1 to 2 times as long as the spikelet on the lower branches. These lower branches are also often reflexed when mature. Inforescences are 5 to 10 cm long and made up of 2 or 3 spikelets: glumes are 8.5 to 13 mm long; lemmas are 4.5 to 8 mm long, half of which are the teeth; awns are
  • Fruit characteristics: Achenes.
  • Leaf characteristics: Blades are commonly flat and somewhat rough to the touch, up to 20 cm long and 2 to 4 cm wide.


  • Blooming phenology: April to May
  • Fruiting phenology: early to late summer
  • Optimum time to identify: The optimal identification period for this species is late spring


  • Growth form: Graminoid
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated species: Agrostis alba, Phleum pratense, Poa compressa, Festuca rubra, Potentilla canadensis, Rumex acetosella, Solidago rugosa, Aster umbellatus, and Pteridium aquilinum.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

Flattened Oatgrass (Danthonia compressa) is on the "watch list." Watch list species have experienced, or are believed to have experienced, a statewide or range wide decline, but they are not currently tracked in the Natural Heritage Inventory (NHI) database. The watch list includes newly discovered species for which origin and rarity need to be determined, certain animals designated as Species of Greatest Conservation Need (SGCN) in the Wisconsin Wildlife Action Plan, and species that were tracked in the past but proved more abundant, widespread or less vulnerable than previously thought. Although watch list species are not actively tracked by NHI, occurrences documented during surveys are often stored by NHI, as these species could be tracked in the future if there is further evidence of their decline.

Summary Information
State Statusnone
Federal Status in Wisconsinnone
State RankSU
Global RankG5
Tracked by NHIW

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 dry hardwood forests and meadows.
  • Soils:

Natural communities

This table lists the natural communities that are associated with Flattened Oatgrass. 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

Ecological landscapes

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

Map of the Ecological Landscapes of Wisconsin.

Ecological landscape score

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.

  • No avoidance measures have been developed for this species.

Management guidance

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

  • No guidance has been developed for this species.


Flattened Oatgrass Photo.

Photo © Steve Janke.

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