Biorepository Data Portal

Herbs, perennial, cespitose, to (3--)7--9 dm. Cataphylls 1--2. Leaves basal, 2--3(--5); auricles transparent, 2--3.5 mm at summit of leaf sheath, apex acutish, membranous; blade flat, (10--)20--30 cm x 0.5--2.3 mm, margins entire. Inflorescences 10--100-flowered, diffuse; internodes of monochasia greater than 6 mm, primary bract usually exceeding inflorescence. Flowers: pedicels 0.1--0.3(--3) mm; bracteoles 2; tepals green, lanceolate, 3.2--4.5 x 0.7--1 mm; outer and inner series nearly equal, in fruit apically erect; stamens 6, filaments 0.8--1.1 mm, anthers 0.3--0.7 mm; style 0.2 mm. Capsules tan, 1-locular, widely ellipsoid to obovoid, 2--3.2 x 1.1--1.6 mm. Seeds tan, ellipsoid, 0.33--0.556 mm, not tailed. 2n = 80. Flowering and fruiting spring. Exposed or partially shaded sites in moist or seasonally wet, sandy or clay soils; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.

Perennial grasslike forb 30 - 90 cm tall Leaves: two to four, basal, 15 - 30 cm long, 0.5 - 2.3 mm wide, slender, grasslike, flattened in cross section, and lacking crosswise partitions inside (non-septate). The leaves also have a fragile, easily broken, transparent, membranous, basal, 2 - 3.5 mm long, pointed-tipped, ear-like appendage (auricle) at the top of the clear-edged leaf sheath. Inflorescence: a terminal, widely spreading, often flat-topped, forked, multi-branched structure with ten to one hundred, single, short-stalked (0.1 - 0.5 mm), radially symmetric, small flowers at the ends of at least 0.6 cm long secondary branches. The entire branched inflorescence is subtended by a large (usually longer than full inflorescence), erect or ascending bract, and the individual stalked flowers have two small bracts (bracteoles) positioned directly below the tepals. Stamens: six, with 0.8 - 1.1 mm long filaments, and 0.3 - 0.7 mm long anthers. Pistil: with one superior ovary, a 0.2 mm long style, and three stigmas. Fruit: single-chambered, tan, 2 - 3.2 mm tall (obviously shorter than tepals), 1.1 - 1.6 mm wide, widely ellipsoid to inversely egg-shaped, distinctly stalked capsules borne widely spaced along spreading branches. Each capsule is surrounded by the erect, remnant tepals. Stems: tufted, erect, smooth, round in cross section. Seeds: many, tan, 0.3 - 0.6 mm long, ellipsoid with short-pointed or abruptly narrowed tips, but without distinct narrowed tails at the ends. Tepals: six in two whorls of three, green, 3.2 - 4.5 mm long (all about same length), 0.7 - 1 mm wide, lance-shaped with pointed tips.

Similar species: Juncus anthelatus is most similar to J. tenuis, but that species is typically smaller (rarely to 70 cm tall), and it has taller capsules (3.3 - 4.4 mm) borne on shorter and more congested inflorescence branches. Also very similar are J. dudleyi and J. interior, except neither of those species have long, pointed, fragile ear-like appendages (auricles) at the summit of the leaf sheaths, rather the auricles are well under 1 mm long and hard or even leathery. Other species such as J. vaseyi and J. greenei differ by having leaves that are almost round in cross section. The non-native J. compressus should be obviously differentiated by its much shorter auricles (only up to 0.5 mm), blunt-tipped tepals, and darker colored capsules.

Flowering: spring

Habitat and ecology: Not common, typically in moist or seasonally wet and usually sandy soil.

Occurence in the Chicago region: native

Notes: Older treatments often consider this species as a variety of J. tenuis, to which it is very closely related and often confused.

Etymology: Juncus is the classical name for Rush. Anthelatus is Latin for "bring in advance" or "place before".

Author: The Field Museum