Juncus inflexus L.

Common Name: European meadow rush

Synonyms and Other Names:

Blue rush, blue arrow rush, hard rush, incurved rush, Juncus glaucus Ehrhart

Pethan Houten (commons.wikimedia.org)Copyright Info

Identification: Juncus inflexus is a perennial species that tends to grow in dense monoculture tufts. This plant has sheathed stalks, blue-green cylindrical stems (40–80 cm × 1.2–4 mm), and interrupted pith (stem tissue). There are several reddish brown cataphylls (leaves that provide the plant with protection and/or structural support) that closely embrace the stems and can be 1–13 cm long.

Juncus inflexus has rhizomes that can extend for 3–5 mm and produce smooth, cyclindrical stems ranging from 1.5–3 mm in diameter.
This species has pedicellate flowers (single multiflowered inflorescence per plant) with ovate bracteoles; the tepals (petals) are reddish brown, lance-like in shape, and can be 2.7–3.5 mm. The margins of the flowers are smooth. Flowers contain 6 stamens with filaments ranging from 0.8–1.5 mm and anthers ranging from 0.8–1 mm, and a style that is 0.3 mm long. Seeds are amber to brown, obliquely ovoid to oblong, not tailed, approximately 0.6 mm in length, and contain veins which are 0.3–0.5 mm. Diploid (2n) individuals have 20, 38, or 40 chromosomes.

Size: Height 1-1.5 feet, Spread 1-2 feet (Missouri Botanical Garden 2012)

Native Range: Eurasia

Map Key
This map only depicts Great Lakes introductions.

Great Lakes Nonindigenous Occurrences: 1st Great Lakes sighting 1922 in the Lake Ontario drainage.  It is now found in MA, MI, NJ, NY, PA, VA in the United States and Ontario in Canada.

Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Juncus inflexus are found here.

State/ProvinceYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
Michigan193620083Black-Macatawa; Keweenaw Peninsula; Southcentral Lake Superior
New York192220084Great Lakes Region; Lake Ontario; Oneida; Seneca

Table last updated 9/30/2019

† Populations may not be currently present.

Ecology: Juncus inflexus can be found in ecosystems with wet soils, including ditches, sandy/peaty hillsides, marshes, dune-slacks, wet meadows, and along the banks of streams, rivers, and lakes, and can grow in up to three inches of water. It prefers neutral or basic soils and has a slight sensitivity to increased iron concentrations (Adamus et al. 2001). It prefers full sun, but will tolerate some shade (Missouri Botanical Garden 2012).

Juncus inflexus typically blooms and fruits between June and September. While this species can produce viable seed, it primarily grows by rhizomal growth (Missouri Botanical Garden 2012).

Juncus inflexus is a hardy species that can tolerate urban pollution and will regrow if cut back to the root (Chalet Nursery 2012, Missouri Botanical Garden 2012). Under ideal conditions, J. inflexus can live up to 8 years (Chalet Nursery 2012).

Means of Introduction: Deliberate release (USEPA 2008).

Status: Established

Great Lakes Impacts:  

Juncus inflexus has a moderate environmental impact in the Great Lakes.
Once this species establishes in an ecosystem, it will likely persist (Stuckey 1981 in Vincent and Cusick 1998). In wetland environments, rushes will out-compete other plant species (Stevens and Hoag 2003).

Juncus inflexus tends to have a significant presence in the seed bank in areas of intensive agriculture (Reiné et al. 2004).

Juncus gerardii poses a competitive threat to the native and naturalized Juncus spp. in the Great Lakes, especially those listed as threatened or endangered, including J. alpinus auct. non Vill., J. ambiguus Guss., J. balticus Willd., J. biflorus Elliot, J. marginatus Rostk. var. biflorus (Elliot) Alph. Wood, J. brachycarpus Engelm., J. brachycephalus (Engelm.) Buchenau, J. dichotomus Elliot, J. diffusissimus Buckley, J. ensifolius Wikstr., J. greenei Oakes & Tuck., J. interior Wiegand, J. militaris Bigelow, J. pelocarpus E. Mey., J. scirpoides Lam., J. secundus P. Beauv. ex Poir., J. stygius L., J. stygius L. ssp. americanus (Buchenau) Hultén, J. subcaudatus (Engelm.) Coville & S.F. Blake, J. vaseyi Engelm. (USDA NRCS 2012c).

Juncus inflexus also poses a genetic threat, because hybrids with J. effusus are possible when these species grow in the same location (Clifford 1958). Several species of this genus have synchronous flowering to attract pollinators, which creates potential for outcrossing (Michalski and Durka 2007).

In the United Kingdom, the roots of Juncus spp. have been observed to trap water and alter the hydrology in shallow water environments (Centre for Aquatic Plant Management 2004).

There is little or no evidence to support that Juncus inflexus has significant socio-economic impacts in the Great Lakes.
Many Juncus spp. serve as a host for larvae of Coquillettidia, a genus of mosquitoes that can serve as a vector for various animal- and human-borne vectors (Sérandour et al. 2010).

Juncus inflexus may be confused with or pose a competitive threat to native rushes that are culturally important, including J. arcticus ssp. littoralis and J. effusus (USDA NRCS 2012b).

There is little or no evidence to support that Juncus inflexus has significant beneficial effects in the Great Lakes.
Juncus inflexus can be planted in rain gardens and for erosion control (Missouri Botanical Garden 2012).

After 20 days of exposure, J. inflexus was able to remove all 100 mg/L of ethylene glycol dinitrate (EGDN), an explosive ingredient in dynamite, from in vitro regenerants (Podlipná et al. 2010). However, when exposed to 500 mg/L, J. inflexus began to die (Podlipná et al. 2008).

Numerous animals feed on the seeds of rushes, including waterfowl, songbirds, quail, cottontail, muskrat (also feeds on roots and rhizomes), porcupine, and other small mammals (Martin 1951 in Stevens and Hoag 2003). Juncus spp. provide habitat for amphibians and various wetland birds, as well as spawning ground for some fish species (Stevens and Hoag 2003).

Cattle, horses, and sheep will graze on Juncus spp., but their specific value as fodder is unknown (Centre for Aquatic Plant Management 2004, Cosyns et al. 2005).

The rhizome matrix can support numerous bacteria that are useful in wastewater treatment (Stevens and Hoag 2003).

Management: Regulations (pertaining to the Great Lakes region)
There are no known regulations for this species.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Aphids may occasionally feed on Juncus spp., but most rushes are fairly resilient to extensive damage from insect or diseases (Stevens and Hoag 2003). Cattle, horses, and sheep graze on Juncus spp., but the extent of control gained from grazing is unknown (Centre for Aquatic Plant Management 2004, Cosyns et al. 2005).

Juncus inflexus will regrow if it is cut or mowed; therefore, these methods will only provide control if done repeatedly (Missouri Botanical Garden 2012).
The rhizome matrix of Juncus spp. enables them to withstand periods of drought and flooding; water level fluctuation is not recommend as a physical control method (Stevens and Hoag 2003).

Sethoxydim will target most grass species and should not affect nearby broadleaf herbs, sedges, or woody plants (IPAW 2012). Glyphosate and ammonium salt of imazapyr will control J. inflexus, but are non-selective and should be applied carefully (Centre for Aquatic Plant Management 2004). Glyphosate should be sprayed directly onto foliage in mid-late summer (Centre for Aquatic Plant Management 2004).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

Remarks: Hybrids: - Juncus balticus x Juncus inflexus occurs as 3 large patches of strongly rhizomatous completely sterile clones in South & West Lancs; 2 of them (South Lancs) are very tall (to 2m) and have an interrupted pith as in J. inflexus, the other (West Lancs) is close to J. inflexus in height but has a continuous pith; all 3 clones 2n=84; endemic.- Juncus x diffusus Hoppe (= J inflexus x Juncus effusus) occurs sporadically with the parents, usually as isolated plants, within the range of J. inflexus. The stems are not glaucous and have continuous pith, intermediate anatomy, and inflorescence shape ± as in J. inflexus; fertility low. Chromosome number: 2n=42.

References: (click for full references)

Adamus, P., T.J. Danielson, and A. Gonyaw. 2001. Indicators for Monitoring Biological Integrity of Inland, Freshwater Wetlands: A survey of North American Technical Literature (1990-2000). U.S. Environmental Protection Agency, Office of Water, Office of Wetlands, Oceans, and Watersheds. Washington, DC. 219 pp.

Centre for Aquatic Plant Management. 2004. Information Sheet 2: Reeds, Rushes, Grasses and Sedges. Centre for Ecology & Hydrology, Natural Environment Research Council. Wallingford, Oxfordshire, United Kingdom. 2 pp.

Chalet Nursery. 2012. Blue Arrows Rush. Plant Finder. Available http://plants.chaletnursery.com/12120004/Plant/5419/Blue_Arrows_Rush. Accessed 26 July 2012.

Clifford, H.T. 1958. On putative hybrids between Juncus inflexus L. and Juncus effusus L. Kew Bulletin 13(3): 392–395.

Cosyns, E., S. Claerbout, I. Lamoot, and M. Hoffmann. 2005. Endozoochorous seed dispersal by cattle and horse in a spatially heterogeneous landscape. Plant Ecology 178(2): 149–162.

Evergreen Native Plant Database. http://www.evergreen.ca/nativeplants/search/view-plant.php?ID=06352 

Flora of North America.  2008.  www.eFloras.org.

Interactive Flora of NW Europe. http://ip30.eti.uva.nl/bis/flora.php?menuentry=soorten&id=4267 

Invasive Plants Association of Wisconsin (IPAW). 2012. Herbicides for Weed Brush Control in Natural Areas. Available http://www.ipaw.org/herbicides.aspx. Accessed 23 July 2012.

Martin, A.C., H.S. Zim, and A.L. Nelson. 1951. American wildlife and plant: A guide to wildlife food habits. Dover Publications, Inc., New York, NY. 500 pp.

Michalski, S.G., and W. Durka. 2007. Synchronous pulsed flowering: analysis of the flowering phenology in Juncus (Juncaceae). Annals of Botany 100: 1271–1285.

Missouri Botanical Garden. 2012. Juncus inflexus. Gardening Help. Available http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/plant-finder/plant-details/kc/u310/juncus-inflexus-afro.aspx. Accessed 26 July 2012.

Podlipná, R., Z. Fialová, and T. Vanek. 2008. Toxic effect of nitroesters on plant tissue cultures. Plant Cell, Tissue and Organ Culture 94: 305–311.

Podlipná, R., Z. Fialová, and T. Vanek. 2010. Degradation of nitroesters by plant tissue cultures. Journal of Hazardous Materials 184(1–3): 591–596.

Reiné, R., C. Chocarro, and F. Fillat. 2004. Soil seed bank and management regimes of semi-natural mountain meadow communities. Agriculture, Ecosystems & Environment 104(3): 567–575.

Sérandour, J., J. Wilson, W. Thuiller, P. Ravanel, G. Lempérière, and M. Raveton. 2010. Environmental drivers for Coquillettidia mosquito habitat selection: a method to highlight key field factors. Hydrobiologia 652: 377 — 388.

Stevens, M., and S. Hoag. 2003. Baltic Rush Juncus balticus Willd. Plant Guide. United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS). 5 pp.

Stuckey RS. 1981. Distributional history of Juncus compressus (Juncaceae) in North America. Canadian Field-Naturalist 95:167–171.

United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS). 2012a. The PLANTS Database. Available http://plants.usda.gov/java/. Accessed 23 July 2012.

United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS). 2012b. The PLANTS Database. Culturally Significant Plants. Available http://plants.usda.gov/java/factSheet?cultural=yes  Accessed 23 July 2012.

United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS), PLANTS Team. 2012c. The PLANTS Database. Threatened & Endangered. Available http://plants.usda.gov/threat.html. Accessed 23 July 2012.

U.S. Environmental Protection Agency (USEPA). 2008. Predicting future introductions of nonindigenous species to the Great Lakes. Washington, DC. 138 pp.

Vincent, M.A. and A.W. Cusick. 1998. New records of alien species in the Ohio vascular flora. Ohio Journal of Science 98(2): 10–17. Available https://kb.osu.edu/dspace/bitstream/handle/1811/23775/V098N2_010.pdf?sequence=1


Other Resources:
Author: Cao, L., L. Berent, and A. Fusaro

Contributing Agencies:

Revision Date: 9/23/2012

Citation for this information:
Cao, L., L. Berent, and A. Fusaro, 2020, Juncus inflexus L.: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?SpeciesID=2699&Potential=N&Type=0&HUCNumber=DGreatLakes, Revision Date: 9/23/2012, Access Date: 2/23/2020

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.