Herbs, perennial, 10--20(--30) cm. Leaves linear-attenuate, 2--6(--9) cm, apex filiform-terete. Inflorescences: scape sheaths slightly longer or slightly shorter than leaves, loose; scapes linear, 0.5--1 mm wide, 4--5-ribbed; mature heads dull gray or lead-colored, rarely straw-colored, hemispheric to subglobose, 3--4 mm wide, mostly nearly glabrous; receptacle glabrous; outer involucral bracts usually not reflexed, not obscured by braceteoles and perianth, straw-colored, greenish, or light gray to gray, dull, ovate to suborbiculate or obovate, 2 mm, margins often erose or lacerate, apex blunt, glabrous; inner bracts, receptacular bracteoles grayish, cuneate to narrowly obovate, 2 mm, margins often erose or lacerate, apex obtuse, glabrous or with a few white hairs abaxially at apex. Staminate flowers: sepals 2, gray, linear to oblong or oblanceolate, 2 mm, apex obtuse, glabrous or with a few white hairs abaxially at apex; androphore club-shaped; petals 2, triangular, minute, white-hairy; stamens 4; anthers black. Pistillate flowers: sepals 2, gray, oblong or oblanceolate, 2 mm, scarious, apex obtuse, abaxially hairy apically; petals 2, yellow-white, spatulate, 2 mm, apex obtuse, glabrous or with a few white, club-shaped hairs apically, adaxially; pistil 2-carpellate. Seeds red-brown, ovoid to broadly ellipsoid, 0.5(--7) mm, with delicate reticulum of horizontally oriented alveolae. Flowering summer--fall. Muddy tidewater banks, brackish marsh, mud flats; 0--100 m; Que.; Conn., Del., Maine, Md., Mass., N.J., N.Y., N.C., Va. A considerable amount of transitional material occurs between Eriocaulon parkeri and E. aquaticum at places along coastal streams where brackish habitat meets more acid habitat upstream.
Much like no. 1 [Eriocaulon aquaticum (Hill) Druce]; scapes 4-5-ridged, tending to be straight, often 2-4 from the same rosette; heads a bit smaller, mostly 3-4 mm thick, hemispheric, the outer invol bracts very pale, dull gray or stramineous, tending to remain ascending even at maturity; perianth and receptacular bracts with few or no hairs; 2n=48. Tidal flats and muddy shores, often submerged, in fresh to slightly brackish water; Me. and Que. to Mass. and c. N.Y., and s. near the coast to N.C. July-Oct.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.