Identification: Juncus compressus is a perennial graminoid (grass-like) herb, about 80 cm in height. Rhizomes are short-creeping or densely branching. When densely branching, the plant appears cespitose (grows in tufts). There are 1-3 cataphylls, and 1-2 leaves, which are basal and cauline (belonging to the stem), with scarious to membranous auricles 0.3-0.5 mm in length. The leaf blade is flat to slightly channeled, measuring 5-35 cm long and 0.8-2 mm wide, with margins entire (without toothing or division). Inflorescences consist of 5-60 flowers, measure 1.5-8 cm, and are lax, and loose to moderately congested. The primary bract usually exceeds the inflorescence. Individual flowers have two bracteoles, and tepals that are brownish, ovate to oblong, and measure 1.7-2.7 mm. Inner and outer tepal series are nearly equal, with the apex obtuse. Flowers have six stamens, with filaments measuring 0.5-0.7 mm and anthers 0.6-1 mm. The style measures about 0.3 mm. Seed capsules are brown or darker, pseudo-3-locular, widely ellipsoid to obovoid, and measure 2.5-3.5 x 1.4-1.8 mm, exceeding the tepals. Individual seeds are light brown, ellipsoid to lunate, measuring 0.35-0.556 mm, and are not tailed. Chromosome number is 2n = 44.
Juncus compressus is easy to confuse with J. gerardii, another non-native species in the Great Lakes (Online Atlas of British & Irish Flora 2012).
† Populations may not be currently present.
* HUCs are not listed for states where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).
References: (click for full references)
Benvenuti, S. 2007. Weed seed movement and dispersal strategies in the agricultural environment. Weed Biology and Management 7:141—157. Available http://onlinelibrary.wiley.com/doi/10.1111/j.1445-6664.2007.00249.x/pdf
Brickell, C. (ed.) 2003. RHS A-Z Encyclopedia of Garden Plants. Third edition. Dorling Kindersley, London.
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.
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. 2012. Juncus compressus. Available http://nativeplants.evergreen.ca/search/view-plant.php?ID=01291. Accessed 23 July 2012.
Flora of North America. 2008. www.eFloras.org
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, New York. 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.
Online Atlas of British & Irish Flora. 2012. Juncus compressus (Round-fruited Rush). Available http://www.brc.ac.uk/plantatlas/index.php?q=plant/juncus-compressus. Accessed 23 July 2012.
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.
Skoglund S.J. 1989. Seed dispersal agents in two regularly flooded river sites. Canadian Journal of Botany 68:754—760.
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, R.S. 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.
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
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.