Nomenclature
Scientific Name:
Equisetum arvense L., Sp. Pl. 1061 (1753)
Synonymy:
Lectotype (selected by Jonsell & Jarvis 1994): Clayton 341, BM 000062951
Etymology:
From the Latin arvensis (pertaining to cultivated fields), a reference to its native habitat in Europe.
Vernacular Name(s):
field horsetail
 Description

Aerial stems dimorphic.  Sterile stems erect, 100–800 mm high, 1–5 mm in diameter, green, usually regularly branched, with undivided lateral branches arising in whorls; main stem occasionally producing terminal strobili in mid-summer; stem ridges nearly smooth; grooves 4–14; central hollow < half the diameter of the stem; leaf sheaths green with brown tips, 4–10 mm long.  Fertile stems 95–275 mm high, 1–3 mm in diameter, pale brown, lacking chlorophyll, unbranched; normally appearing in spring before the sterile stems, and dying after shedding spores; leaf sheaths pale green or brown with darker teeth, 9–22 mm long.  Strobili 4–40 mm long, 5–10 mm in diameter, apices obtuse.

 Recognition

Equisetum arvense is recognised by its dimorphic fertile and sterile stems, its abundantly branching vegetative stems that have uniformly green leaf sheaths with 4–14 grooves, and its obtuse strobilus.  It is easily the most common of the species in New Zealand, frequently dominating river-banks and other sites where it has become established.

 Distribution

North Island: Auckland, Gisborne, Taranaki, Southern North Island.

South Island: Western Nelson, Sounds Nelson, Marlborough, Westland, Canterbury, Otago.

Altitudinal range:  0–670 m.

A widespread northern temperate species now extensively naturalised in the Manawatu and Rangitīkei catchments of the North Island, and the Mokihinui and Matiri catchments in the South Island.  It is also naturalised in Auckland, Kāwhia, New Plymouth, Gisborne, Hawke’s Bay, eastern and southern Wairarapa, parts of Marlborough, Christchurch, Ashburton and Otago Peninsula.  It occurs most frequently in lowland sites along river banks, but has been recorded up to 560 m at Mataroa, near Taihape, and 670 m in the Marino Mts, Nelson.

It was first recorded in the wild from Wanganui and was believed to have been introduced with iris rhizomes from Japan (Atkinson 1922).  It has spread from there throughout the Manawatu and Rangitīkei catchments as far as Taihape and Palmerston North.  It is dispersed easily in river shingle and sand, while in urban areas it has spread with other garden plants, or sometimes been misguidedly cultivated.  It now occurs in a substantial part of central New Zealand and will inevitably spread further.

 Habitat

Equisetum arvense occurs most frequently along muddy banks of lakes and rivers, in river shingle and sand, along drains and the edges of swamps, in damp grass, in wet dune hollows, around shingle piles, and as a weed of cultivation in urban areas.  It is an aggressive weed in sandy and muddy soils because of its extensive underground rhizomes, and frequently excludes other vegetation.  It is almost impossible to eradicate once established, and is not readily susceptible to chemical control (James & Rahman 2010).  In urban areas, stems are capable of pushing up through tar seal.

 Biostatus
Exotic
 First Record

Atkinson (1922, p. 290).  Voucher: AK 110803, 1922

 Notes

Equisetum arvense in the Northern Hemisphere has been documented by Hauke (1967), and its coning behaviour in New Zealand described by Brownsey et al. (1985).  In New Zealand E. arvense is an Unwanted Organism.

 Bibliography
Atkinson, E.H. 1922: Weeds and their identification. Field horsetail (Equisetum arvense). New Zealand Journal of Agriculture 25: 290–292.
Biosecurity New Zealand 2012: Regional Pest Management Strategies Database. http://www.biosecurityperformance.maf.govt.nz/
Biosecurity New Zealand 4 Aug 2011: Unwanted Organisms Register. http://www.biosecurity.govt.nz/pests/registers/uor
Brownsey, P.J.; Given, D.R.; Lovis, J.D. 1985: A revised classification of New Zealand pteridophytes with a synonymic checklist of species. New Zealand Journal of Botany 23(3): 431–489.
Brownsey, P.J.; Moss, T.C.; Sneddon, B.V. 1985: Cone production in Equisetum arvense. Wellington Botanical Society Bulletin 42: 16–21.
Brownsey, P.J.; Perrie, L.R. 2015: Equisetaceae. In: Breitwieser, I; Heenan, P.B.; Wilton, A.D. (ed.) Flora of New Zealand — Ferns and Lycophytes. Fascicle 6. Manaaki Whenua Press, Lincoln.
Brownsey, P.J.; Smith-Dodsworth, J.C. 2000: New Zealand ferns and allied plants. Edition 2. David Bateman, Auckland.
Connor, H.E. 1977: The Poisonous Plants in New Zealand. Edition 2. Government Printer, Wellington.
Hauke, R.L. 1967: A systematic study of Equisetum arvense. Nova Hedwigia 13: 81–109.
Howell, C. 2008: Consolidated list of environmental weeds in New Zealand. DOC Research & Development Series 292: 42.
James, T.K.; Rahman, A. 2010: Chemical control of field horsetail (Equisetum arvense). New Zealand Plant Protection 63: 102–107.
Jonsell, B.; Jarvis, C.E. 1994: Lectotypifications of Linnaean names for the Flora Nordica Vol. 1 (Lycopodiaceae - Papaveraceae). Nordic Journal of Botany 14: 145–164.
Linnaeus, C. 1753: Species Plantarum. Impensis Laurentii Salvii, Stockholm.