Juncus effusus
(common rush)

Preferred Scientific Name

• Juncus effusus

Preferred Common Name

• common rush

Other Scientific Names

• Juncus bogotensis Kunth
• Juncus communis E. Mey
• Juncus griscomii Fernald
• Juncus laevis Wallr.
• Juncus polyanthemus BUCHEN.

International Common Names

• English: bog rush; Japanese mat rush; soft rush
• Spanish: junco de esteras; junquera
• French: jonc à lier; jonc diffus; jonc épars
• Chinese: deng xin cao

Local Common Names

• Colombia: junco; junco chiquito; totora; totorilla
• Japan: igusa

EPPO code

• IUNEF (Juncus effusus)

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Cyperales
•                         Family: Juncaceae
•                             Genus: Juncus
•                                 Species: Juncus effusus

Juncus is a genus with a worldwide distribution, consisting of about 300 species (Brooks and Clemants, 2000). J. effusus was described by Linnaeus in 1753. The species has a wide global distribution and exhibits morphological variation across its range. Because of this variation the delineation of species limits and infraspecific taxa has been problematic and controversial. According to Zika (2003), “The Juncus effusus L. complex vexes systematists”.

The Juncus effusus complex consists of J. effusus and close relatives, particularly J. conglomeratus and J. pylaei, although many other species with narrow distributions have been described. Some authors break this complex up into more than one species, e.g. (Hämet-Ahti, 1980; Balslev, 1996; Kirschner, 2002; Weakley, 2016), or treat these taxa at the level of variety (Fernald and Wiegand, 1910). Many subspecies or varieties have also been described including subsp. solutus and others (Hämet-Ahti, 1980; Kirschner, 2002; Zika, 2003). In contrast, some treat it as a highly variable species, lumping all of the above taxa into the single variable species, J. effusus, such as Engelmann (1868), and recently Brooks and Clemants (2000).

Authors who treat the J. effusus complex as a group of 3 species, and with J. effusus consisting of several subspecies, e.g. Hämet-Ahti (1980) and Kirschner (2002), note that some of these taxa have become naturalized outside of their natural ranges. J. conglomeratus, native of the Old World, is naturalized in North America, New Zealand, and Venezuela. J. pylaei, native of northeastern North America, is naturalized in the northwestern USA. J. effusus subsp. effusus, native of the Old World, is naturalized in the Americas, eastern Asia, and Australia. J. effusus subsp. solutus, native to eastern North America, is naturalized in western North America. Complicating matters further, J. effusus forms hybrids with other species, including J. conglomeratus, J. inflexus and J. pallidus (Wilcox, 2010).

Some localized have been described as new species that were later considered introductions of J. effusus. For example, J. luxurians was described from New Zealand, but was later considered to be conspecific with J. effusus which is probably introduced (Edgar, 1964).

The following description has been adapted from Kirschner (2002).

J. effusus is a perennial plant, with culms to 1.5 m tall, densely caespitose with short rhizomes. Stem terete, without leaf blades, green, smooth to inconspicuously ridged; ridges 40-70, pith continuous, cataphylls 3(-4). Inflorescence pseudolateral (appearing lateral), diffuse or rarely dense, of 50-120 separate flowers. Lower bract usually several times longer than inflorescence, appearing as extension of culm. Tepals 1.5-3 mm long, outer ones longest, lanceolate, apiculate, green to light brown with scarious margin. Stamens 3 (-6); anthers 0.4-0.7 mm long, slightly shorter than filaments. Style very short; stigmas 0.6-1 mm long. Capsule (1.61) 2-2.5 mm long, subequal to or slightly exceeding perianth, subspheroid to ovoid, broadly ellipsoid or obovate, obtuse or slightly retuse, not or shortly mucronate, unilocular, triseptate, light brown. Seeds 0.5 × 0.2-0.3 mm, obliquely ovoid, reticulate, without appendages. 

J. effusus was introduced to Australia by 1840 (AVH, 2016), New Zealand by 1871 (Esler and Astridge, 1987) and to Hawaii by 1900 (Wester, 1992). Wagner et al. (1999) states that the species has spread from cultivation in Hawaii.

Soil drainage

• free
• impeded
• seasonally waterlogged

Soil reaction

• acid
• alkaline
• neutral
• very acid

Soil texture

• light
• medium

Natural Dispersal

According to Balslev (1996) swelling of the seed coat when wet causes the inflorescence to turn into heavy, slimy mass, causing the culms to bend to the ground, depositing seeds. The very small seeds have high potential for long-distance dispersal (Michalski and Durka, 2012).

Accidental Introduction

Despite the introduction of J. effusus to new geographic regions, there is little data on causes of introduction. Introductions were probably accidental. Wagner et al. (1999) states that the species has spread from cultivation in Hawaii.

In its native range and introduced range J. effusus is a weed of a variety of wet agricultural habitats, including wet pastures and wet agricultural habitats. In the USA it can invade cranberry production areas and impede drainage in adjacent ditches (Ghantous and Sandler, 2015). It can limit grazing for cattle in poorly drained pastures, which do not graze the species (Bakker et al., 1984; Rana and Sellers, 2009). In Europe it is a weed of fodder plantings, pastures, cereals, and root crops (Weber and Gut, 2005). 

Impact on Habitats

Because of its large stature J. effusus can displace other native species (Ervin and Wetzel, 2002), reducing species diversity. It is a troublesome weed in cutaway peatlands in Europe, outcompeting young conifers that have been planted in restoration programs (McCorry and Renou, 2003).  

Impact on Biodiversity

J. effusus competes with rare species in Hawaii, including three species listed as Endangered by the US Fish and Wildlife Service. These include Phyllostegia hispida in Molokai, Phyllostegia mannii in Molokai and Maui, and Sanicula purpurea in Maui (US Fish and Wildlife Service 2011a,b,c).

• Invasive in its native range
• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Tolerant of shade
• Long lived
• Has high reproductive potential
• Gregarious
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Altered trophic level
• Changed gene pool/ selective loss of genotypes
• Ecosystem change/ habitat alteration
• Modification of successional patterns
• Monoculture formation
• Negatively impacts agriculture
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

• Allelopathic
• Competition - monopolizing resources
• Competition - shading
• Competition (unspecified)

• Highly likely to be transported internationally accidentally
• Difficult to identify/detect as a commodity contaminant
• Difficult/costly to control

Economic Value

Human uses of J. effusus are currently limited. It has been used traditionally for weaving, including material for sleeping mats, chair seats, and baskets, and the pith serves as a wick for candles and lamps (Porcher, 1869; Balslev, 1996). In China the pith is used for drawing hot Camellia oleifera tea seed oil.

Social Benefit

In China, the outer epidermis is used as a wick for applying the oil to the body for relieving pain. The pith is also used as a tranquilizer and diuretic (Eisenberg et al., 2009).