Sagittaria lancifolia subsp. lancifolia Lindl.

Herb, perennial, to 2 m tall, glabrous to sparsely pubescent; rhizomes to 19 x to 4 cm. Leaves emerged; petioles round to triangular, 44-58 x 0.3-2.5 cm, basal sheath to 26 cm long, blade pale green, linear to ovate or elliptic, 20.3-35 x 0.7-16 cm, apex acute, basal lobes absent, veins 7-9. Inflorescence a simple or paniculate scape of 6-13 whorls, emerged, 16-72 x 19-60 cm, whorls with 3 flowers; peduncle triangular, 75-125.5 x 0.3-1.5 cm; bracts united, coarse, striate to ribbed, staminate bracts elliptic to ovate-elliptic, 3-6 mm long, apex round-acute to acute, carpellate bracts elliptic, 4-32 mm long, apex acute; staminate pedicels spreading, cylindric, 1.9-2.5 x 0.01-0.03 cm; carpellate pedicels spreading, in flower and fruit, to 38 x 0.3-0.4 mm. Staminate flowers: sepals reflexed to spreading, 5.5-6.5 x 3.5-5.2 mm, striate to ribbed, petals clawed, 0.8-1.5 x 0.6-1.2 mm, claws ca. 0.5 mm long, stamens ca. 24, filaments pubescent, cylindric, 2.2-4 x ca. 0.5 mm, anthers linear, 1.7-2.3 x ca. 0.8 mm, apex obtuse, without sterile carpels. Carpellate flowers: sepals reflexed to spreading in flower and fruit, 4-8.4 x 3.4-5.4 mm, striate to ribbed, petal clawed, 0.6-1.5 x 0.4-1.3 cm, claw to 4.5 mm long, without ring of sterile stamens. Fruit aggregate 0.5-1.2 cm diam.; achenes obelliptic, 1.6-2.5 x 0.8-1.1 mm, not tuberculate, with 1 gland, keeled, beak lateral, erect, 0.3-0.7 mm long.

Economic use: Sold as aquarium plants under the German commercial name "Lanzettblättriges Pfeilkraut" ("Lance-leaved Arrowhead").