Juncus effusus

Juncus effusus
Soft rush by a stream
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
(unranked):	Commelinids
Order:	Poales
Family:	Juncaceae
Genus:	Juncus
Species:	J. effusus
Binomial name
Juncus effusus L.

Soft rush (Juncus effusus) is a member of the Juncus genus found growing in wet areas, for example, the purple moor-grass and rush pastures and fen-meadow plant associations in the United Kingdom. It is native to most continents.

Description

Pupal cases of Coleophora caespitiella on J. effusus.

It grows in large clumps about 1.5 meters (5 feet) tall at the water’s edge along streams and ditches, but can be invasive anywhere with moist soil. It is commonly found growing in humus-rich areas like marshes, ditches, fens, and beaver dams.

The stems are smooth cylinders with light pith filling. The yellowish inflorescence appears to emerge from one side of the stem about 20 cm from the top. In fact the stem ends there; the top part is the bract, that continues with only a slight colour-band marking it from the stem. The lower leaves are reduced to a brown sheath at the bottom of the stem.

Distinction from other species

J. effusus can be differentiated from the rarer J. pylaei by the number of ridges on the stem. J. effusus has 30 to 40 ridges and J. pylaei has 10 to 20.^[1]

Differentiation within the Species

Juncus effusus is divided into no fewer than nine varieties, as listed by the USDA PLANTS website. The list presented there includes the following varieties: the 'lamp rush' varieties brunneus, decipiens, exiguus, gracilis, and solutus; 'common rush' varieties conglomeratus, effusus, and pylaei; and 'Pacific rush' pacificus. Many of these have overlapping distributions in the US. The specific details differentiating these varieties are not presented on the USDA PLANTS website, but attribution to specific botanists is given for each variety.

Distribution

It is a common plant native in most temperate countries.

Uses

In Japan this rush is grown to be woven into the covering of tatami mats.

References

Notes

General references

1. Zika, Peter F., The native subspecies of Juncus effusus (Juncaceae) in western North America, April 2003, Brittonia pages 150–156.

External links

• Jepson Manual Treatment
• Photo gallery

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