Ruppia cirrhosa
Widgeon grass
Image of Ruppia cirrhosa

Photo by Robert W. Freckmann 

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Key Characteristics

Small grass-like aquatic of highly calcareous lakes; leaves submerged and thread-like, up to 30 cm long; fruits asymmetrical on short to long stalks.

Status and Rank

  • State Status: T
  • State Rank: S1
  • Global Rank: G5


County NameNumber of OccurrencesYear Last Observed
Distribution map for Ruppia cirrhosa

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.


This largely marine species, which inhabits a diversity of coastal and estuarine habitats, is known in Michigan only from Manistique Lake in the Upper Peninsula, where it occurs in up to 8 feet of water on a peaty substrate.

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

Few associate data are known, as most collections of this species were made from plants uprooted and washed ashore. It has been noted to occur with Chara, a green alga.


This species possibly occurs as a post-glacial relict. Its persistence may be dependent on maintaining lake hydrology and preventing water pollution and potential impacts from excessive recreational activities. This submersed aquatic may possibly occur in other northern Michigan lakes.

General Survey Guidelines

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

Survey Methods

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at [Accessed Aug 16, 2018]


Survey References

Technical References

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