Illinois Natural History Survey - University of Illinois

Diarrhena obovata
Beak grass

Synonyms: Diarrhena americana obovata

Subspecific taxa:


  • Magnoliophyta

Other taxonomic & nomenclature sources: USDA PlantsITISThe Plant ListIPNI

Species Distribution
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County Map Legend
Not known from county
Medium confidence:
Medium or unknown confidence;
often old records or unverifiable observations
Medium-high confidence:
Often observations by expert botanists
High confidence:
Often vouchered herbarium records
Planted / introduced:
Native species introduced outside historic range,
or only in planted locations within county (e.g., restorations)
Historic / extirpated:
Only historic records for the species; likely extirpated
(Note that this category is not yet functional)

North American distribution maps for this species: FLNAUSDA PlantsBONAPBISON

Collections, Observations & Flowering by Month [?]


Collections & Observations by Decade [?]

Species Status

Status/Listing: No Information


Origin: Native

Species Description

General: Monocot, perennial

Roots: adventitious, rhizomes

Shoots: alternate leaf arrangment; simple leaf type; entire leaf margin; Parallel leaf venation; awl-shaped leaf shape

Inflorescence: panicle

Flowers: perfect; 3 merous; complete; hypogynous ovary position

Fruit: grain

Physiology: autotrophic

Reproduction: vegetative

Ecology & Natural History

Habitat: Species is distributed in low, shaded woods; moist ledges, and base of limestone cliffs.

ILPIN Notes: These plants peep their shining dark green foliage well into winter and species is recommended as a ground cover in shady gardens and slopes. Species has a distinctive "bottle-shaped" grain (beaked caryopsis). Versus var. americana, this plant is smaller and glabrous. According to one author, this is "one of the more handsome woodland grasses." Species is found throughout Illinois except in northeast corner.

Functional Relationships:

  • Pollinators:
  • Dispersal:
  • Mycorrhizae:
  • N2 fixation:

Human Relationships:

  • Edibility [?] :
  • Showy Flowers:

Wildlife and Livestock Information:

  • Food Value:
  • Cover Value:

Coefficient of Conservatism (C-value) [?] :

  • Entire State:
  • Chicago Area: 10

Comments & Questions

Post: 09/2017
Which species of Diarrhena am I seeing in the Chicago area?

IL Plant Response:
We have two species recorded for Illinois (D. americana and D. obovata).

For a long time it was thought that Diarrhena americana was restricted to southern Illinois, while D. obovata was statewide (Mohlenbrock 1986, 2002, 2014; Brandenburg in FNA 2007). Now we are starting to see collections labeled as D. americana throughout Illinois. Thus, the distribution of these species in Illinois may still need clarification. It is possible that these more recent records of D. americana in the northern part of the state are planted or introduced from the horticultural trade.

The distribution map for D. americana on the Illinois Plants website is currently not accurate because it includes old records of Diarrhena that were made before these species were recognized as being distinct. Therefore, these older records contain both species under single name that cannot be separated. We hope to fix this problem.

As far as identification, previous floras have used sheath pubescence to separate these species, but newer treatments do not consider that to be a good character. The size and shape of the lemma does seem to be consistent, although it is slightly overlapping.

Other distinguishing features from the genus revision by Brandenburg et al. 1991, published in the Bulletin of the Torrey Botanical Club can be found here.

Diagrams of D.obovata showing the abruptly tapering apex of the lemma and beak of the caryopsis can be seen here:

Here are pictures of D.obovata showing the lemma and the bottlenosed beak of the caryopsis (photo credit P. Marcum, Champaign, IL).

(Note: This response was originally posted on the Midwest Graminoids- Grasses, Sedges, and Rushes Facebook group page, P. Marcum & G. Spyreas)

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