Eleocharis parvula (Roemer & J.A. Schultes) Link ex Bluff, Nees, & Schauer. Dwarf Spikerush, Small Spikerush. Phen: Jul-Sep. Hab: Tidal brackish and freshwater marshes, inland salt marshes, shallow waters of managed impoundments. Dist: NS, NL (Newfoundland), and MI south to c. peninsular FL and LA; BC south to CA; Mexico, Central America, South America, Eurasia, Africa. Reported for s. IN by Bill Thomas (pers.comm., 2022).

Origin/Endemic status: Native

Taxonomy Comments: While many authors have accepted a broad, single taxon concept of E. parvula, others designate two additional taxa: Eleocharis coloradoensis, which occurs from Saskatchewan south to Kansas, and E. parvula var. anachaeta, which occurs from the Great Plains south to Mexico (which includes our flora region); E. parvula may reach its western extent within the United States somewhere within the central (or eastern?) Gulf Coastal Plain, although more work is needed to determine this. Correll and Johnston (1979) mention that var. anachaeta is the dominant variety in Texas (although, see map in Gilly 1941, which although preliminary at the time, seems to disagree somewhat on potential boundaries laid forth by Smith's explanations). I have observed achenes from a small number of specimens spanning these three regions and agree that there is a subtle, but clear distinction between the three taxa (Ward, personal observation). C.L. Gilly designated E. membranacea, a name apparently based upon Torrey's Eleocharis pygmaea (which Gray apparently later designated as synonymous with Chaetocyperus membranaceus), but Gilly's Llano County, TX type lacks achenes, which unfortunately complicates our distinction between the three overall potential taxa (Gilly 1941). Overall, E. coloradoensis in a strict sense differs from E. parvula in having achenes without bristles, oblong tubers, achenes rugulose, and up to 25 scales per spike, and as occurring more primarily from Kansas northward (although if including E. parvula var. anachaeta, then eastward to AL according to Smith's mapping). Eleocharis parvula var. anachaeta, perhaps only occurring within the western portion of our area (eastward to Louisiana?), differs from typical E. coloradoensis by having slightly less rugulose (and potentially shorter?) achenes and with an achene/tubercle confluence that is even more difficult to distinguish, although it still lacks bristles and is seemingly not entirely smooth like E. parvula (Smith et al. 2002; Ward, personal observation). A name would need to be prioritized for this taxon, if recognized at species or varietal level (both of which have been proposed); otherwise, it falls within a very broad concept of E. parvula. Refer to Smith et al. (2002) for more details on section Parvulae. Users of this key in states such as AR, MO, OK, TX, and LA should pay particular attention to these above-mentioned achene characters when finding any plants within the broad E. parvula complex.

Synonymy: = Ar, ETx1, FNA23, G, GW1, Il, K1, K3, K4, Mex, Mi, Mo1, NcTx, NE, NY, Pa, RAB, Tat, Tn, Tx, Va, WH3; = Eleocharis parvula (Roem. & Schult.) Link ex Bluff, Nees, & Schauer var. parvula – C, F; = Scirpus nanus Spreng. – S13, misapplied; > Eleocharis coloradoensis (Britton) Gilly; > Eleocharis parvula (Roem. & Schult.) Link ex Bluff, Nees, & Schauer var. anachaeta (Torr.) Svenson – GrPl; > Eleocharis parvula (Roem. & Schult.) Link ex Bluff, Nees, & Schauer var. coloradoensis (Britton) Beetle; > Eleocharis parvula (Roem. & Schult.) Link ex Bluff, Nees, & Schauer var. parvula – GrPl

Show in key(s)

Show parent genus

Wetland Indicator Status:

• Atlantic and Gulf Coastal Plain: OBL
• Eastern Mountains and Piedmont: OBL
• Great Plains: OBL
• Midwest: OBL
• Northcentral & Northeast: OBL

Heliophily: 9