Sparganium acaule (Beeby ex Macoun) Rydberg. Phen: May-Sep. Hab: Bogs, stream margins. Dist: NL (Newfoundland) and c. QC west to s. AB and WA, south to w. NC, IN, IA.

Origin/Endemic status: Native

Taxonomy Comments: Ito et al. (2016) resurrected S. acaule from synonymy or infraspecific association under S. emersum, based on morphology and its phylogenetic relationship with S. glomeratum (as opposed to the relationship of S. emersum s.s. with S. angustifolium). Some skepticism remains; however, in validating whether or not S. acaule merely represents a smaller growth form of what was formerly called S. emersum var. acaule, but would now be recognized as S. chlorocarpum var. acaule at variety level. If not recognized as distinct at species level, then this latter variety name would take precedent; if not even recognized at varietal rank, then S. chlorocarpum Rydb. would take precedence.

Synonymy: = Sparganium chlorocarpum Rydb. var. acaule (Beeby ex Macoun) Fernald – F; = Sparganium emersum Rehmann ssp. acaule (Beeby ex Macoun) C.D.K.Cook & M.S.Nicholls – Cook & Nicholls (1986); = Sparganium emersum Rehmann var. acaule (Beeby ex Macoun) A.Haines – NE; < Sparganium chlorocarpum Rydb. – C, G, RAB, W, WV, Beal (1960), Thieret (1982); < Sparganium emersum Rehmann – AqW, FNA22, Il, K3, K4, Pa, Va, Crow & Hellquist (2000b)

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Wetland Indicator Status:

• Eastern Mountains and Piedmont: OBL (name change)
• Great Plains: OBL (taxonomic split from wetland indicator species)
• Midwest: OBL (taxonomic split from wetland indicator species)
• Northcentral & Northeast: OBL (taxonomic split from wetland indicator species)

Heliophily: 8