Sagittaria filiformis J.G. Sm.
Habitat: Shallow, swift waters or deep streams [Open water (non-forested, wetland)]
Range: Maine south to Florida.
Aids to Identification: Narrow-leaf arrowhead is a submerged aquatic perennial with submersed and floating leaves. The floating leaves are linear-ovate to ovate in shape and 0.5 cm wide. The long, submerged, ribbon-like leaves are usually over 30 cm in length. The petiole, which connects the leaf to the stem, is flattened. The flowers are white, with 3 petals, and are borne in racemes with 2-4 whorls of flowers.
Ecological characteristics: Found in shallow waters of slow moving rivers in Maine.
Phenology: Flowering summer through fall.
Synonyms: Sagittaria stagnorum Small.; Sagittaria subulata (L.) Buch. var. gracillima (S. Wats.) J.G.Sm.
Known Distribution in Maine: This rare plant has been documented from a total of 10 towns in the following counties: Cumberland, Kennebec, Sagadahoc, Somerset.
Reason(s) for rarity: At northern edge of range.
Conservation considerations: Invasive aquatic plants or impoundment could pose a threat to populations.