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Description: Leaves: submersed or emersed. Submersed leaves are 6.4 - 35 cm long, 0.5 - 10 cm wide, and linear. Emersed leaves on triangular stalks 6.5 - 17 cm long, with linear to egg-shaped or elliptic blade 2.5 - 17.4 cm long and 0.2 - 4 cm wide. Inflorescence: emersed, singly stalked along a central axis (raceme), or with loosely branched stalks (panicle), 2.5 - 21 cm long, 1 - 8 cm wide, arising from a stalk 3 - 50 cm long, with one to twelve whorls of flowers. Bracts:3 - 15 mm long, broadly awl-shaped to lance-shaped, coarse, fused at least one-quarter the length. Flowers:either male or female, found on the same plant (monoecious), to 2.3 cm wide, with a stalk longer than 1 cm, three recurved to spreading sepals 3 - 6 mm long, and three white or pink petals 1 - 2 cm long. Male flowers are borne near the top of the inflorescence, having scaly filaments shorter than the anthers. Female flowers found near bottom of inflorescence, with spreading fruiting stalks 0.5 - 5 cm long. Fruit:a cluster of achenes 0.6 - 1.5 cm wide. Each achene is 1.5 - 3 mm long, 1.1 - 1.5 mm wide, narrow and inversely egg-shaped, with a horizontal beak 0.1 - 0.3 mm long. Sagittaria graminea has established in two western Washington lakes. It is growing densely and inhibiting the growth of native aquatic species. Its occurrence in two widely separated lakes indicates that people are deliberately planting this species in Washington. Sagittaria graminea is a noxious weed in both New Zealand and Australia causing serious problems in shallow waterways. It appears that this species is seriously weedy when introduced outside of its native range. Jenifer Parsons has also seen Sagittaria rigida here in Washington in Crocker Lake in Jefferson County. However, Sagittaria ridida does not appear to be nearly as weedy as S. graminea.
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