This variable species has both terrestrial and aquatic forms, sometimes divided into separate varieties. Terrestrial plants grow 7–39 inches tall in moist soils with simple or branching stems, while aquatic plants float on the surface with stems up to 10 feet long rooting in the bottom mud. Stems can be hairless to hairy. Note the elliptical to lance-shaped leaves up to 6 inches long, and the dense, erect, cylindrical spikes of tiny pink to red flowers. The plant spreads by rhizomes and can form colonies.

FLOWER: June–September. Single or paired, dense, cylindrical, erect spikes of reddish to pinkish-white flowers on branch ends (not leaf axils); flowers 1/4 inch long (4–6 mm) with 5 petal-like tepals, anthers reddish, extending beyond the petals. Water based plants produce short spikes 3/8–1 1/2 inches long (1–4 cm), while flower clusters of terrestrial plants in moist soil reach 1 1/2–4 5/8 inches long (4–11 cm).

LEAVES: Alternate, on stalks (petioles) to 1 1/4 inches long (3 cm). Blades elliptic to lance-shaped, 3/4–6 inches long (2–15 cm); margins entire, surfaces hairy or smooth without dark blotches, tips pointed to rounded. Sheaths around stem at leaf nodes tan, paper-like to leaf-like, hairless or with hairs, top edge flared or tight against stem.

HABITAT: Moist sandy, silty soils, shallow water; river and lake shorelines, ponds, wet ditches, drainages, moist prairies and meadows.

ELEVATION: 4,200–9,600 feet.

RANGE: All states west of Mississippi River, Great Lake and New England states.

SIMILAR SPECIES: The aquatic or wet habitat and terminal, single to paired, pinkish flower clusters helps distinguish this species from the 7 other smartweeds in NM.

NM COUNTIES: Widespread in NM in low- to high-elevation wet habitats: Bernalillo, Catron, Chaves, Cibola, Colfax, Curry, De Baca, Dona Ana,  Harding, Hidalgo, Lincoln, Los Alamos, Luna, McKinley, Mora, Rio Arriba, San Juan, San Miguel, Sandoval, Santa Fe, Sierra, Socorro, Taos, Union, Valencia.