Stems 11--75 cm ´ 0.1--0.8 mm. Leaves 0.3--2.8 mm; sheath 1--1.9 mm wide, apex rounded; blade 0.2--1.8 mm wide, teeth 50--100 per side, invisible to unaided eye, apex acute to mucronate. Flowers 1--3 per axil. Staminate flowers 1.5--2.5 mm; anther 4-loculed. Pistillate flowers 1.5--2 mm. Seeds 1.2--2.5 ´ 0.4--0.6 mm; aeroleareoles of testa in 20 longitudinal rows. 2n = 24.

Flowering early summer--fall. Lakes, rivers, and canals; 0--1500 m; Alta., Ont. Que.; Ala., Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis.; Mexico; West Indies; Central America; South America.

Annual submersed aquatic herb to 0.8 m long

Leaves: opposite, stalkless, 0.3 - 2.8 cm long, 0.2 - 1.8 mm wide, widening to a 1 - 1.9 mm sheath at base, linear with an abruptly pointed tip, with 50 to 100 tiny teeth per side (may require hand lens).

Flowers: either male or female, found on the same plant (monoecious), borne one to three in leaf axils, green, tiny. The 1.5 - 2.5 mm long male flowers have four-lobed beaks, and the 1.5 - 2 mm long female flowers have four-lobed stigmas and stout styles to 0.5 mm long.

Fruit: achene-like, yellowish white with a hint of purple, 1.2 - 2.5 mm long, 0.4 - 0.6 mm wide, spindle-shaped (fusiform), dull, pitted in ten to twenty rows.

Stems: slender, highly branched, 11 cm - 0.75 m long, 0.1 - 0.8 mm wide, rooting at the nodes.

Similar species: Other subspecies of Najas guadalupensis differ from this subspecies by having longer styles (0.7 - 1.5 mm) and seeds with 30 - 60 rows of pits.

Flowering: early summer to fall

Habitat and ecology: Occasional in shallow water of ponds and lakes.

Occurence in the Chicago region: native

Etymology: Najas comes from the Greek name for a river nymph, naias. Guadalupensis means "from Guadalupe Island, Mexico."

Author: The Morton Arboretum

This species is found in lakes and is restricted to our lake area. I have never taken notes concerning the habitats of this or the preceding species, but all that I have collected were found on sandy or marly bottoms in less than 4 feet of water.