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Peter F. Zika, except as noted

Annual, perennial herb generally from rhizomes. Stem: round or flat. Leaf: generally basal; sheath margins fused, or overlapping and generally with 2 ear-like extensions at blade junction; blade round, flat, or vestigial, glabrous or margin hairy. Inflorescence: head-like clusters or flowers 1, variously arranged; bracts subtending inflorescence 2, generally leaf-like; bracts subtending inflorescence branches 1–2, reduced; bractlets subtending flowers generally 1–2, generally translucent. Flower: generally bisexual, radial; sepals and petals similar, persistent, green to brown or ± purple-black; stamens generally 3 or 6, anthers linear, persistent; pistil 1, ovary superior, chambers generally 1 or 3, placentas 1 and basal or 3 and axile or parietal, stigmas generally > style. Fruit: capsule, loculicidal. Seed: 3–many, generally with white appendages on 1 or both ends.
7 genera, 440 species: temperate, arctic, and tropical mountains. [Kirschner 2002 Species Plantarum: Fl World, vols. 6–8 (Juncaceae). ABRS] Flowers late spring to early fall. —Scientific Editors: Douglas H. Goldman, Bruce G. Baldwin.
Unabridged references: [Balslev, H. 1996. Juncaceae. Flora Neotropica Monograph 68: 1–168. New York Botanical Garden, Bronx, NY; —Brooks, R. E. and S.E. Clemants. 2000. Juncus. In: Flora of North America Editorial Committee, Eds. Flora of North America North of Mexico. Volume 22, Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford University Press, New York. Pages 211–255; —Brooks, R. E. and A.T. Whittemore. 1999. Juncus anthelatus (Juncaceae, Juncus subg. Poiophylli), a new status for a North American taxon. Novon 9:11–12; —Catling, P. M. and K.W. Spicer. 1987. The perennial Juncus of section Poiophylli in the Canadian prairie provinces. Canadian Journal of Botany 65: 750–760; —Ceska A. 2001. Juncaceae. In: Douglas, G. W., D. Meidinger, and J. Pojar, Eds. Illustrated Flora of British Columbia, Volume 6, Monocotyledons (Acoraceae Through Najadaceae). British Columbia Ministry of Environment, Lands and Parks, Ministry of Forests, Victoria, British Columbia, Canada; —Clemants, S. E. 1990. Juncaceae (Rush Family) of New York State. New York State Museum Bulletin No. 475, Albany, NY; —Cope, T. A. and C.A. Stace. 1978. The Juncus bufonius L. aggregate in western Europe. Watsonia 12: 113–128; —Drábková, L., J. Kirschner, O. Seberg, G. Petersen and C. Vlcek. 2003. Phylogeny of the Juncaceae based on rbcL sequences, with special emphasis in Luzula DC. and Juncus L. Plant Systematics and Evolution 240: 133–147; —Drábková, L., J. Kirschner and C. Vlcek. 2002. Comparison of seven DNA extraction and amplification protocols in historical herbarium specimens of Juncaceae. Plant Molecular Biology Reporter 20: 161–175; —Drábková, L., J. Kirschner, C. Vlcek and V. Paces. 2004. TrnL-trnF intergenic spacer and trnL intron define major clades within effusus aggregateuzula and Juncus (Juncaceae): importance of structural mutations. Journal of Molecular Evolution 59: 1–10; —Ertter, B. 1986. The Juncus triformis complex. Memoirs of the New York Botanical Garden 39: 1–89; —Hämet-Ahti, L. 1980. The Juncus effusus aggregate in eastern North America. Annales Botanici Fennici 17: 183–191; —Harriman, N. A. and D. Redmond. 1976. Somatic chromosome numbers for some North American species of Juncus L. Rhodora 78: 727–738; —Hermann F. J. 1964. The Juncus mertensianus complex in western North America. Leaflets of Western Botany 10: 81–87; —Hermann F. J. 1975. Manual of the Rushes (Juncus species) of the Rocky Mountains and Colorado Basin. USDA Forest Service, General Technical Report RM-18, Fort Collins, CO; —Johnson, L. A. S. 1963. New species of Juncus in Australia and New Zealand. Contributions from the New South Wales National Herbarium 3: 241–244; —Jokerst, J. 1986. A new Juncus from Chile. Fremontia 14(2): 22–23; —Kirschner, J., Ed. 2002. Juncaceae 1: Rostkovia to Luzula, Species Plantarum: Flora of the World Part 6. Australian Biological Resources Study, Canberra, Australia. 237 p; —Kirschner, J., Ed. 2002. Juncaceae 2: Juncus subg. Juncus, Species Plantarum: Flora of the World Part 7. Australian Biological Resources Study, Canberra, Australia. 336 p; —Kirschner, J., Ed. 2002. Juncaceae 3: Juncus subg. Agathryon, Species Plantarum: Flora of the World Part 8. Australian Biological Resources Study, Canberra, Australia. 192 p; —Lamont, E. E. and S.M. Young. 2005. Juncus diffusissimus, an addition to the flora of New York, with notes on its recent spread in the United States. Journal of the Torrey Botanical Society 132: 635–643; —Lint, H. L. 1977. A revision of Juncus subgenus Genuini (Juncaceae) in the Pacific States. Unpublished Ph.D. Dissertation, Oregon State University, Corvallis; — Munro, S. L. and H.P. Linder. 1998. The phylogenetic position of Prionium (Juncaceae) within the Order Juncales based on morphological and rbcL sequence data. Syst Bot 23: 43–55; —Plunkett, G. M., D.E. Soltis, P.S. Soltis, and R.E. Brooks. 1995. Phylogenetic relationships between Juncaceae and Cyperaceae: insights from rbcL sequence data. 1995. American Journal of Botany 82: 520–525; —Roalson, E. H. 2005. Phylogenetic relationships in the Juncaceae inferred from nuclear ribosomal DNA internal transcribed spacer sequence data. International Journal of Plant Sciences 166: 397–413; —Snogerup, S. 1978. Notes on Juncus for Flora Europaea. Botaniska Notiser 131: 185–187; —Snogerup, S. 1980. Juncaceae. Pp. 102–116. In: Tutin, T. G., V.H. Heywood, N.A. Burges, D.M. Moore, D.H. Valentine, S.M. Walters and D.A. Webb, eds. 1980. Flora Europaea, Vol. 5, Alismataceae to Orchidaceae (Monocotyledones). Cambridge Univ. Press, Cambridge, UK. 452 p; —Snogerup, S. 1993. A revision of Juncus subgen. Juncus (Juncaceae). Willdenowia 23: 23–73; —Snogerup, S., P.F. Zika, and J. Kirschner. 2002. Taxonomic and nomenclatural notes on Juncus. Preslia 74: 247–266. [Available at:] Stace, C. A. 1970. Anatomy and taxonomy in Juncus subgenus Genuini. Botanical Journal of the Linnean Society 63 (suppl. 1): 75–84; —Stuckey, R. L. 1980. The migration and establishment of Juncus gerardii (Juncaceae) in the interior of North America. Sida 8: 334–347; —Van Loenhoud, P. J. and A.A. Sterk. 1976. A study of Juncus bufonius complex in the Netherlands. Acta Botanica Neerlandica 25: 193–204; —Witham, C. W. and P.F. Zika. 2008. Juncus digitatus (Juncaceae), a new annual rush from Shasta County, California, U.S.A. Journal of the Botanical Research Institute of Texas 2: 775–781; —Zika, P. F. 2003. The native subspecies of Juncus effusus (Juncaceae) in western North America. Brittonia 55: 150–156; —Zika, P. F. 2006. A key to Juncus section Juncotypus in British Columbia. Botanical Electronic News No. 358, February 27, 2006. [Available at:]]

Key to Juncaceae

Rhizome 0 or generally with scale-like leaves. Stem: generally cylindric or flat. Leaf: blade well developed and cylindric or flat, occasionally closely resembling stem, or reduced to small point; crosswalls generally present; appendages generally present at blade-sheath junction. Inflorescence: generally terminal, appearing lateral when pushed aside by inflorescence bract; bractlets 0–2. Flower: sepals, petals similar; stamens generally 3 or 6(2); pistil 1, ovary chambers 1–3, placentas axile or parietal, stigmas generally 3(2). Seed: many.
315 species: worldwide, especially northern hemisphere. (Latin: to join or bind, from use of stems) [Ertter 1986 Mem New York Bot Gard 39:1–90] All species with leaf crosswalls may have leaves, stems swollen, deformed by sucking insects. Fruiting time given instead of flowering time. Juncus bulbosus L., Juncus dichotomus Elliott, and Juncus elliotti Chapm. reportedly naturalized in California.

Key to Juncus

J. cooperi Engelm. COOPER'S RUSH (Group 2)
Perennial herb, ± cespitose, 40–80 cm; rhizome short, thick, many-branched; roots large, spongy. Leaf: basal; blades short, stiff, cylindric, tips sharp. Inflorescence: appearing lateral; lowest bract cylindric, resembling stem, > inflorescence, tip sharp; branches unequal; clusters 2–10-flowered; bracts within inflorescence obvious, > cluster; bractlets white. Flower: perianth parts 4–6 mm, sepals > petals, pale ± green-straw-colored, sepal tips generally acuminate, spiny, firm; stamens 6, large, filaments < anthers. Fruit: ± = perianth, narrowly oblong, 3-angled. Seed: with a conspicuous white ridge; appendages unequal, minute.
Alkaline places; < 700 m. Desert; Nevada, Mexico. May–Oct [Online Interchange] {CNPS list}

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora,, accessed on Apr 18 2014
Citation for this treatment: [Author of taxon treatment] 2012. Juncus, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on Apr 18 2014

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Bioregions in which Juncus cooperi occurs Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
map of distribution 1
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.