Sagittaria filiformis J.G. Smith. clade: Graminea Group, Platyphylla Complex. Threadleaf Arrowhead. Phen: May-Sep. Hab: Swiftly flowing water of blackwater rivers and streams, blackwater lake shores, tidal waters. Dist: As conceived here, probably ranging from MA south to s. FL, s. AL, and s. MS.

ID notes:The forms growing in swiftly flowing black water are remarkable and unlikely to be recognized as a Sagittaria unless in flower, with linear leaves over 100 cm long and only 1-3 mm wide, with 5-7 parallel ribbed veins, resembling S. kurziana.

Origin/Endemic status: Native

Taxonomy Comments: The proper taxonomic treatment and associated nomenclature to apply to these plants has been uncertain and controversial (see synonymy).

Synonymy: = AqW, FNA22, K1, K3, NE, NY, Pa, Va, WH3, Keener (2005); = n/a – Tat; = Sagittaria stagnorum Small – GW1; = Sagittaria subulata (L.) Buchenau var. gracillima (S.Watson) J.G.Sm. – F, G, RAB, Bogin (1955); > Sagittaria filiformis J.G.Sm. – S; >< Sagittaria kurziana Glück – SFla; > Sagittaria lorata Chapm. – S, S13; > Sagittaria stagnorum Small – S, SFla; < Sagittaria subulata (L.) Buchenau – C

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Wetland Indicator Status:

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

Heliophily: 8