Culms to 28 cm. Floral scales brown, streaked with green on flanks. Flowers: perianth bristles to 2 times as long as achene, rarely shorter than achene. Achenes green to golden brown when ripe, 0.5-1.1 × 0.4-0.8 mm, apex often highly constricted proximal to tubercle. Tubercles 0.3-0.7 × 0.2-0.4 mm. 2n = 20.

Fruiting summer-winter (Jun-Nov). Bogs, cold springs, dry stream banks, lake and pond margins, maritime mud flats, marshes, moist meadows, swamps; 0-1000 m; N.B., N.S., Ont., Que.; Ark., Conn., Del., Fla., Ga, Ill., Ind., La., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tex., Vt., Va., Wis.

Eleocharis flavescens var. olivacea was reported from Hawaii; I have not seen a voucher specimen.

Perennial herb with slender, creeping rhizomes, mat-forming 3 - 28 cm tall

Leaves: reduced to bladeless sheaths, basal, two per culm, margins fused and enclosing culm, translucent, long and thin, inflated towards the blunt apex, membranous, usually wrinkled, often disintegrating.

Flowers: minute, spirally arranged on the axis of the spikelet, lacking sepals and petals, with zero to eight (usually seven) bristles, subtended by a scale. Bristles (when present) whitish to straw-colored, usually longer than the achene. Stamens three, exserted. Anthers to 1 mm long. Pistil one. Style typically two-cleft.

Fruit: a one-seeded achene, green to yellowish brown, about 0.5 - 1 mm long and 0.5 mm wide, reverse egg-shaped to reverse pear-shaped, lenticular (lens-shaped), often constricted at the apex, finely wrinkled (at 40X). Tubercle pale, small, basally swollen, shortly conic. Seed with a thin, non-adherent wall.

Spikelets: solitary, 1.5 - 9 mm long, 1 - 3.5 mm wide, egg-shaped or ellipsoidal with a more or less pointed apex, with up to 65 floral scales. Scales spirally arranged and overlapping, brown with green-streaked flanks, 1 - 3 mm long, about 0.5 - 1.5 mm wide, egg-shaped or elliptical with a more or less pointed apex, membranous.

Culms: widely spreading, unbranched, 3 - 28 cm long, about 0.5 mm wide, compressed, often spongy, enclosed basally by two fused sheaths.

Similar species: No information at this time.

Flowering: late June to late September

Habitat and ecology: Rare in the Chicago Region. Has been found in the wet areas of lakes in mud, sand, peat, and marl.

Occurence in the Chicago region: native

Etymology: Eleocharis comes from the Greek words heleios, meaning "dwelling in a marsh," and charis, meaning grace. Flavescens means "turning yellow." Olivacea means "olive green" or "olive brown."

Author: The Morton Arboretum