Juncus acuminatus Michaux var. robustus Engelmann; J. robustus (Engelmann) Coville 1896, not S. Watson 1879

Herbs, perennial, cespitose, 3--10 dm. Roots without terminal tubers. Culms erect, terete, 4--6 mm diam., smooth. Cataphylls 1--2, straw-colored, apex acute. Leaves: basal 1--2, cauline 1--2; auricles 1.2--1.5 mm, apex rounded, scarious; blade straw-colored or green, terete, 20--65 cm x 1.1--3.5 mm, with prominent and conspicuous ringlike bands at position of cross partitions; distal cauline leaves reduced to 2.5 cm. Inflorescences terminal panicles of 30--250 heads, 8--12 cm, branches spreading; primary bract erect to ascending; heads 2--10-flowered, broadly obovoid to hemispheric, 0.3--0.5 mm diam. Flowers: tepals straw-colored, lance-subulate, apex acuminate; outer tepals 1.9--2.2 mm; inner tepals 1.7--2.1 mm; stamens 3, anthers equal filament length. Capsules exserted, straw-colored, 1-locular, ovoid, 1.9--2.5 mm, apex acute, valves separating at dehiscence. Seeds oblong or ellipsoid, 0.5--0.6 mm, not tailed; body clear yellow-brown.

Fruiting late spring--late summer. Commonly in shallow water, marshy shores, sloughs, wet flatwoods, and savannas, bogs, ditches, wet woods, shores, in standing water to 3 ft 1 m deep; 100--200 m; Ala., Ark., Fla., Ill., Ind., Kans., Ky., La., Mo., Okla., Tenn., Tex.