Juncus acutus
Environmental Weed (2024)
Common names
sharp rush
Biostatus
Exotic
Category
Vascular
Structural class
Rushes & Allied Plants
Simplified description
Upright spiny rush to 1 m tall, with tall cylindrical sharp tipped, stems and leaves forming dense stiff clumps, with clumped flowerheads near the end of each stem, made up of many red-brown to orange flowers/capsules (fruit).
Flower colours
Brown, Orange
Detailed description
Very stout, forming dense prickly tufts; rhizomes stout, woody. Stems (40–)60–100 cm × 1.5–5 mm, very stiff and erect, smooth, light green. Basal sheaths shining dark red-brown. Leaves 1–2, basal, terete, similar to stem, with very pungent tip. Inflorescence large, compact 5–15 cm long. Flowers crowded. Tepals c. 3 mm long, ± equal, very hard, outer mucronate, inner truncate to emarginate with wide membranous margin at tip. Stamens 6. Capsule 4.5–5 mm long, much > tepals, ovoid, abruptly tapered, acute, reddish-brown to brownish-orange. Seeds with distinct tails.
Similar taxa
No other rush has a combination of leaves similar to the stem, sharp pointed and large (> 4 mm) red-brown to orange capsules in a dense clustered head.
Distribution
Scattered, but locally abundant in Northland, Auckland, Manawatu and Wellington, mostly coastal.
Habitat
Wet and seasonally dry sandy areas
Conservation status
Not applicable
Detailed taxonomy
Family
Taxonomic notes
Subgenus Juncus, Section Juncus(Thalasii) Kirschner (2002: Juncaceae 2)
Ecology
Flowering
Summer
Fruiting
Autumn
Year naturalised
1923
Origin
Europe, Africa, North and South America
Reason for introduction
Unknown, seed or soil contaminant.
Control techniques
Can be controlled manually, mechanically or herbicidally depending on situation.
Life cycle and dispersal
Perennial. Seed dispersed by animals, water or contaminated machinery.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
FACW: Facultative Wetland
Usually is a hydrophyte but occasionally found in uplands (non-wetlands).
Other information
Etymology
juncus: From the Latin jungere ‘to tie or bind’, the stems of some species being used to make cord (Johnson and Smith)
Environmental Weed (2024)
This plant is named in a list of 386 environmental weeds in New Zealand 2024 prepared by DOC. 759 candidate species were considered for inclusion on this new comprehensive list of environmental weeds in New Zealand. The species considered were drawn from published lists of weed species, lists of plants that must be reported or managed by law if observed, existing national and regional programmes and agreements for pest management, and species already managed by the Department of Conservation (DOC). Candidate species were then assessed to see if they were fully naturalised and whether they have more than minor impacts in natural ecosystems. Read the full report here.
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
JUNACS
Referencing and citations
References and further reading
Champion, P. et al. 2020. Freshwater Invasive Species of New Zealand 2020. NIWA publication. https://docs.niwa.co.nz/library/public/FreInSpec.pdf
Healy, A. J. 1982. Identification of weeds and clovers. New Zealand Weed and Pest Control Society Publication. Editorial Services Limited, Featherston. 299 p.
Healy, A. J.; Edgar, E. 1980. Flora of New Zealand, Volume III. Adventive Cyperaceous, Petalous and Spathaceous Monocotyledons. Government Printer, Wellington. 220 p.
Johnson, A. T.; Smith, H. A. 1986. Plant Names Simplified: Their pronunciation, derivation and meaning. Landsman Bookshop Ltd, Buckenhill, UK.
Johnson, P. N.; Brooke, P. A. 1989. Wetland plants in New Zealand. DSIR Field Guide, DSIR Publishing, Wellington. 319 p.
Kirschner, J. (compiler) 2002. Juncaceae 2: Juncus subg. Juncus, Species Plantarum: Flora of the World Part 7: 1–336.
Attribution
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA). Features description from Healy and Edgar (1980).
Some of this factsheet information is derived from Flora of New Zealand Online and is used under a Creative Commons Attribution 3.0 New Zealand licence.