Plants monoecious, perennial or rarely annual, glabrous to sparsely pubescent, growing submersed, floating-leaved, or emerged in fresh or brackish waters. Roots septate. Stems often with rhizomes; rhizomes occasionally terminated by tubers, tubers brown, smoothLeaves submersed, floating, or emerged, sessile or petiolate, petioles terete to triangular, blades present or absent, linear to rhombiform to sagittate, without pellucid markings. Inflorescences erect, racemose or paniculate scapes, emerged or floating, rarely submersed, whorls 1-17, each whorl with 2-3 flowers; bracts coarse or delicate, smooth to papillose, obtuse to acute; pedicels elongating after anthesis, ascending to recurved; carpellate flowers in lower part of inflorescences, staminate flowers above. Flowers unisexual, rarely lower ones with a ring of sterile stamens, pedicellate; sepals herbaceous to coriaceous, often sculptured, reflexed in staminate flowers, reflexed to appressed in carpellate flowers; petals white or rarely with a pink to purple spot or tinge; stamens 7-many, filaments linear to dilated, glabrous to pubescent, anthers basifixed, linear to orbicular; gynoecium of many carpels, carpels 1-ovuled, styles terminal. Achenes compressed, with a conspicuous dorsal wing, not ribbed, glandular.
Argentina present, Asia present, Canada present, Chile present, Guianas present, predominently Western Hemisphere present
A predominently Western Hemisphere genus of ca. 20 species, from Canada S to Argentina and Chile; 3 or 4 species also occur in Europe and Asia; 3 species in the Guianas.
Bogin (1955) combined
Sagittaria and Lophotocarpus, recognizing 2 subgenera:
Sagittaria: ascending to reflexed sepals and mostly spreading to ascending pedicels in fruit, and all flowers unisexual.
Lophotocarpus: appressed sepals and recurved pedicels in fruit, and upper flowers bisexual.