Juncus cooperi Engelm.

Herbs, perennial, robust, tufted, 4--10 dm. Rhizomes short. Culms terete, 1.5--2.5 mm diam. Cataphylls several, reddish brown, often apiculate. Leaves basal, 1--2; auricles essentially absent; blade terete, 10--40 dcm, shorter than culm. Inflorescences glomerules 3--12, each with (1--)2--5 flowers, open, branches unequal, 3--12 cm, primary bract terete or slightly compressed, shorter to longer than inflorescence. Flowers: tepals straw-colored to pale green, ovate-lanceolate, 4--5 mm, apex acuminate or setaceous; inner series elliptic, nearly equal, margins wide, scarious, apiculate; stamens 6, filaments 1 mm, anthers 1.5--2 mm; style 1 mm. Capsules tan to light reddish brown, 3-locular, ellipsoid, 3.7--4.5 x1.6--2 mm, mostly shorter than or nearly equal to perianth. Seeds dark amber, obovoid, body 0.7--1 mm, tails 0.1--0.5 mm.

Ariz., Calif., Nev., Utah; Mexico.

Flowering and fruiting spring--summer.

Saline flats and meadows or edges of salt marshes; below 600m.

Juncus cooperi is a species of rush known by the common name Cooper's rush. It is native to the deserts of the southwestern United States and northern Mexico, where it grows in alkaline and saline soils such as those around salt marshes and desert springs. This is a perennial herb forming large clumps of erect stems up to about 80 centimetres tall from a thick rhizome and large root network. The bases of the stems are surrounded by sparse, small leaves, which are stiff and have sharp tips. The inflorescence is a cluster of brown, pale green, or straw-colored flowers accompanied by one bract which appears as an extension of the stem.

Juncus cooperi là một loài thực vật có hoa trong họ Juncaceae. Loài này được Engelm. mô tả khoa học đầu tiên năm 1868.