Sparganium americanum Nuttall. American Bur-reed. Phen: May-Sep. Hab: Streams, marshes, ponds, pools, spring branches, often submerged. Dist: NL (Newfoundland) west to MN, south to c. peninsular FL and c. TX.

Origin/Endemic status: Native

Taxonomy Comments: Beal (1960) discusses the interesting variation in S. americanum, perhaps worthy of taxonomic recognition. The ‘Appalachian Race’ has stigmas 0.6-0.9 mm long, inflorescence branches 0-3, and relatively narrow leaves; in our area it is montane in distribution, and in general is Appalachian, Ozarkian, and northern. The ‘Coastal Race’ has stigmas 1.5-2.8 mm long, 2-5 inflorescence branches, and relatively wide leaves; in our area it is primarily of the Coastal Plain, disjunct to the mountains of NC and SC south of the Asheville Basin (like many Coastal Plain taxa), and in general is nearly limited to the Coastal Plain, ranging from MA south to FL, west to e. TX, and north in the interior to sc. TN, s. IN, and s. MO. The ‘Ubiquitous Race’ is intermediate, with stigmas 1.0-1.4 m long; it occurs throughout the range of the species. The pattern is suggestive of imperfect evolutionary separation of two taxa and needs additional study and likely taxonomic recognition of entities.

Synonymy: = Ar, C, ETx1, F, FNA22, G, GW1, Il, K1, K4, Mi, Mo1, NE, NY, Pa, RAB, S, Tat, Tn, Tx, Va, W, WH3, WV, Beal (1960), Cook & Nicholls (1986), Crow & Hellquist (2000b), Thieret (1982)

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