Eleocharis geniculata (L.) Roem. & Schult.
Common Name: SPIKE-RUSH
Synonym: Eleocharis caribaea
Coefficient of Conservatism: 9
Coefficient of Wetness: -5
Wetness Index: OBL
Physiognomy: Nt A-Sedge
Status: X
Eleocharis geniculata A. A. Reznicek

E. caribaea of Michigan Flora.

Wet sandy, marly borders of ponds in northwestern Washtenaw Co. and northeastern Jackson Co.

This is a widespread tropical species, occurring into the southern United States and disjunct in the southern Great Lakes region. Not seen in Michigan since 1937, but still present very locally on or near Lake Erie in SW Ontario, NW Ohio, NW Pennsylvania and the Lake Michigan shore region of Illinois and Indiana.

The disjunct Great Lakes area plants were long ago described as a distinct species, Eleocharis dispar E. J. Hill, with purple-tinted scales, whereas tropical plants have basically straw colored or greenish scales. If recognized at all, this is now considered only a variety, but more study is needed.

With their purple scales (and small spikelets), our plants might seem to resemble the recently resurrected Eleocharis microformis Buckley from the southwest (O’Kennon & Taylor, 2013). However, the spikelets are many flowered, and the achenes are larger and with narrow tubercles in our plants.



Jackson County
Washtenaw County


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. June 29, 2022. https://michiganflora.net/species.aspx?id=1108.