Brief Summary

Equisetum, which includes around 15 extant species, is the only extant genus of horsetails or scouring rushes (Equisetophyta, Sphenophyta, Arthrophyta, and Equisetaceae are among the names that have been used for this group. The horsetails are now believed to form a monophyletic group with the ferns that is known as the "monilophytes" (although the position of the horsetails within the monilophytes is not yet fully resolved, they may be nested among other ferns);  this clade, in turn, is the sister group to the seed plants (Pryer et al. 2001; Schneider et al. 2009 and references therein; Rai and Graham 2010 and references therein). Equisetum is nearly cosmopolitan (not native to Australia and New Zealand, but they are exotic weeds there). Many Equisetum have a high silica content and can be used to scour pots (explaining the name "scouring rush"). Horsetails have an extensive and diverse fossil record and several hundred million years ago widespread tree-sized relatives reached 30 m in height (even today, some Equisetum species can reach an impressive size--although nothing approaching 30 m!).

(Mabberley 2008)

For more information on the biology of horsetails, see Husby (2013) and  Chad Husby's website.

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Comprehensive Description


Terrestrial perennial plants with creeping subterranean rhizomes, roots borne in whorls at the nodes. Aerial stems erect, green, hollow, jointed, conspicuously ribbed,with whorls of branches at the nodes.the branches themselves also jointed. Leaves reduced to a many-toothed short sheath at each node. Cones (sporangiophores) borne at the ends of the main vegetative stems and rarely the branches too.   
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Foodplant / saprobe
Cryptococcus aquaticus is saprobic on dead stem of Equisetum

Foodplant / open feeder
larva of Dolerus aericeps grazes on frond of Equisetum
Other: sole host/prey

Foodplant / open feeder
larva of Dolerus bimaculatus grazes on frond of Equisetum
Other: sole host/prey

Foodplant / open feeder
larva of Dolerus germanicus grazes on frond of Equisetum
Other: sole host/prey

Foodplant / open feeder
larva of Dolerus gessneri grazes on frond of Equisetum
Other: sole host/prey

Foodplant / open feeder
larva of Dolerus pratensis grazes on frond of Equisetum
Other: sole host/prey

Foodplant / open feeder
larva of Dolerus yukonensis grazes on frond of Equisetum
Other: sole host/prey

In Great Britain and/or Ireland:
Foodplant / saprobe
fruitbody of Flagelloscypha kavinae is saprobic on dead stem of Equisetum

Foodplant / feeds on
larva of Grypus equiseti feeds on Equisetum

Foodplant / feeds on
larva of Hippuriphila modeeri feeds on Equisetum

Foodplant / saprobe
superficial, scattered on in small groups, thinly subiculate perithecium of Hydropisphaera arenula is saprobic on dead stem of Equisetum
Remarks: season: 1-12

Foodplant / saprobe
fruitbody of Lachnella alboviolascens is saprobic on dead stem (large) of Equisetum

Foodplant / open feeder
larva of Loderus eversmanni grazes on frond of Equisetum
Other: sole host/prey

Foodplant / open feeder
larva of Loderus gilvipes grazes on frond of Equisetum
Other: sole host/prey

Foodplant / open feeder
larva of Loderus pratorum grazes on frond of Equisetum
Other: sole host/prey

Foodplant / open feeder
larva of Loderus vestigialis grazes on frond of Equisetum
Other: sole host/prey

Foodplant / saprobe
loosely gregarious, covered, the piercing the epidermis pycnidium of Stagonosporopsis coelomycetous anamorph of Stagonosporopsis equiseti is saprobic on dead sheath of Equisetum


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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records:344
Specimens with Sequences:328
Specimens with Barcodes:319
Species With Barcodes:26
Public Records:184
Public Species:24
Public BINs:0
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Barcode data

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Equisetum (/ˌɛkwɨˈstəm/; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds.[2]

Equisetum is a "living fossil" as it is the only living genus of the entire class Equisetopsida, which for over one hundred million years was much more diverse and dominated the understory of late Paleozoic forests. Some Equisetopsida were large trees reaching to 30 meters tall.[3] The genus Calamites of the family Calamitaceae, for example, is abundant in coal deposits from the Carboniferous period.

A superficially similar but entirely unrelated flowering plant genus, mare's tail (Hippuris), is occasionally misidentified as "horsetail".

It has been suggested that the pattern of spacing of nodes in horsetails, wherein those toward the apex of the shoot are increasingly close together, inspired John Napier to discover logarithms.[4]

Etymology[edit source | edit]

Microscopic view of Rough Horsetail, Equisetum hyemale (2-1-0-1-2 is one millimetre with 1/20th graduation).
The small white protuberances are accumulated silicates on cells.

The name "horsetail", often used for the entire group, arose because the branched species somewhat resemble a horse's tail. Similarly, the scientific name Equisetum derives from the Latin equus ("horse") + seta ("bristle").

Other names include candock for branching individuals, and snake grass or scouring-rush for unbranched or sparsely branched individuals. The latter name refers to the rush-like appearance appearance of the plants, and to the fact that the stems are coated with abrasive silicates, making them useful for scouring (cleaning) metal items such as cooking pots or drinking mugs, particularly those made of tin. In German, the corresponding name is Zinnkraut ("tin-herb"). Rough horsetail E. hyemale is still boiled and then dried in Japan, to be used for the final polishing process on woodcraft to produce a smoother finish than any sandpaper.

Distribution, ecology and uses[edit source | edit]

The genus Equisetum is near-cosmopolitan, being absent only from Antarctica. They are perennial plants, either herbaceous and dying back in winter as most temperate species, or evergreen as most tropical species and the temperate species rough horsetail (E. hyemale), branched horsetail (E. ramosissimum), dwarf horsetail (E. scirpoides) and variegated horsetail (E. variegatum). They typically grow 0.2-1.5 m tall, though the "giant horsetails" are recorded to grow as high as 2.5 m (northern giant horsetail, E. telmateia), 5 m (southern giant horsetail, E. giganteum) or 8 m (Mexican giant horsetail, E. myriochaetum), and allegedly even more.[5]

Many species in this genus prefer wet sandy soils, though some are semi-aquatic and others are adapted to wet clay soils. The stalks arise from rhizomes that are deep underground and almost impossible to dig out. The field horsetail (E. arvense) can be a nuisance weed, readily regrowing from the rhizome after being pulled out. It is also unaffected by many herbicides designed to kill seed plants. However, as E. arvense prefers an acid soil, lime may be used to assist in eradication efforts to bring the soil pH to 7 or 8.[6] Members of the genus have been declared noxious weeds in Australia and in the US state of Oregon.[7][8]

All the Equisetum are classed as "unwanted organisms" in New Zealand and are listed on the National Pest Plant Accord.

Vegetative stem:
B = branch in whorl
I = internode
L = leaves
N = node

If eaten over a long enough period of time, some species of horsetail can be poisonous to grazing animals, including horses.[9] The toxicity appears to be due to thiaminase enzymes, which can cause thiamine deficiency.[10][11][12][13] People have regularly consumed horsetails. The young plants are eaten cooked or raw, but considerable care must be taken. Horsetail is dangerous for individuals with edema.[14] For example, the fertile stems bearing strobili of some species are cooked and eaten like asparagus (a dish called tsukushi[15]) in Japan.[16] The people of ancient Rome would eat meadow horsetail in a similar manner, but they also used it to make tea as well as a thickening powder.[17] Indians of the North American Pacific Northwest eat the young shoots of this plant raw.[18] The plants are used as a dye and give a soft green colour. An extract is often used to provide silica for supplementation. Horsetail was often used by Indians to polish wooden tools. Equisetum species are often used to analyze gold concentrations in an area due to their ability to take up the metal when it is in a solution.[17]

Anatomy[edit source | edit]

Strobilus of Northern Giant Horsetail (Equisetum telmateia braunii), terminal on an unbranched stem.

In these plants the leaves are greatly reduced and usually non-photosynthetic. They contain a single, non-branching vascular trace, which is the defining feature of microphylls. However, it has recently been recognised that horsetail microphylls are probably not ancestral as in Lycopodiophyta (clubmosses and relatives), but rather derived adaptations, evolved by reduction of megaphylls.[19] They are, therefore, sometimes actually referred to as megaphylls to reflect this homology.

The leaves of horsetails are arranged in whorls fused into nodal sheaths. The stems are green and photosynthetic, and are distinctive in being hollow, jointed and ridged (with sometimes 3 but usually 6-40 ridges). There may or may not be whorls of branches at the nodes.

Spores[edit source | edit]

The spores are borne under sporangiophores in strobili, cone-like structures at the tips of some of the stems. In many species the cone-bearing shoots are unbranched, and in some (e.g. field horsetail, E. arvense) they are non-photosynthetic, produced early in spring separately from photosynthetic, sterile shoots. In some other species (e.g. marsh horsetail, E. palustre) they are very similar to sterile shoots, photosynthetic and with whorls of branches.

Horsetails are mostly homosporous, though in the field horsetail smaller spores give rise to male prothalli. The spores have four elaters that act as moisture-sensitive springs, assisting spore dispersal after the sporangia have split open longitudinally.

Systematics[edit source | edit]

Species[edit source | edit]

The living members of the genus Equisetum are divided into two distinct lineages, which are usually treated as subgenera. Hybrids are common, but hybridization has only been recorded between members of the same subgenus.[20]

In addition, there are numerous ill-determined populations. One of them, the Kamchatka Horsetail (Equisetum camtschatcense),[verification needed] is an ornamental forming imposing stands of these archaic plants.

Subgenus Equisetum
Branched Horsetail (E. ramosissimum)
Subgenus Hippochaete
unplaced to subgenus

Named hybrids[edit source | edit]

Hybrids between species in subgenus Equisetum
Hybrids between species in subgenus Hippochaete

Equisetum cell walls[edit source | edit]

The crude cell extracts of all Equisetum species tested contain mixed-linkage glucan : Xyloglucan endotransglucosylase (MXE) activity.[21] This is a novel enzyme and is not known to occur in any other plants. In addition, the cell walls of all Equisetum species tested contain mixed-linkage glucan (MLG), a polysaccharide which, until recently, was thought to be confined to the Poales.[22][23] The evolutionary distance between Equisetum and the Poales suggests that each evolved MLG independently. The presence of MXE activity in Equisetum suggests that they have evolved MLG along with some mechanism of cell wall modification. The lack of MXE in the Poales suggests that there it must play some other, currently unknown, role. Due to the correlation between MXE activity and cell age, MXE has been proposed to promote the cessation of cell expansion.

Medicinal uses[edit source | edit]

The plant has a long history of medicinal uses, although modern sources include cautions with regard to its use.[24] The European Food Safety Authority issued a report assessing its medicinal uses in 2009.[25] Equisetum telmateia may be a useful source of antioxidants.[26]

See also[edit source | edit]

References[edit source | edit]

  1. ^ "Equisetum thermale sp. nov. (Equisetales) from the Jurassic San Agustín hot spring deposit, Patagonia: anatomy, paleoecology, and inferred paleoecophysiology". American Journal of Botany 98 (4): 680–97. April 2011. doi:10.3732/ajb.1000211. PMID 21613167. 
  2. ^ Sunset Western Garden Book, 1995:606–607
  3. ^ "An Introduction to the Genus Equisetum and the Class Sphenopsida as a whole". Florida International University. Retrieved 2009-07-22. 
  4. ^ Sacks, Oliver (August 2011). "Field Trip: Hunting Horsetails". The New Yorker. 
  5. ^ Husby, Chad E. (2003): How large are the giant horsetails? Version of 2003-03-19. Retrieved 2008-11-20.
  6. ^ Kress, Henriette, Getting rid of horsetail, Henriette's Herbal Homepage, April 7th, 2005. Retrieved May 19, 2010.
  7. ^ William Thomas Parsons, Eric George Cuthbertson (2001). Noxious weeds of Australia. CSIRO Publishing. p. 14. ISBN 978-0-643-06514-7. 
  8. ^ "Equisetum telmateia Ehrh. giant horsetail". USDA. Retrieved 2010-05-18. 
  9. ^ Israelsen, Clark E.; McKendrick, Scott S. & Bagley, Clell V. (2006): Poisonous Plants and Equine. PDF fulltext
  10. ^ Henderson, JA; Evans EV, McIntosh RA. (June 1952). "The antithiamine action of Equisetum.". J Am Vet Med Assoc. 120 (903): 375–8. PMID 14927511. Retrieved 3 February 2013. 
  11. ^ Fabre, B; Geay B, Beaufils P. (1993). "Thiaminase activity in equisetum arvense and its extracts.". Plant Med Phytother 26: 190–7. 
  12. ^ "Horsetail". National Library of Medicine. Retrieved 3 February 2013. 
  13. ^ Pohl, Richard (1955). "Toxicity of ferns and equisetum". American Fern Journal 45 (3): 95–97. 
  14. ^ citation|url=http://www.pfaf.org/user/Plant.aspx?LatinName=Equisetum+arvense%7Ctitle=Plants for a future: Equisetum arvense
  15. ^ Michael Ashkenazi, Jeanne Jacob. 2003. Food culture in Japan. Greenwood Publishing Group. 232 p.
  16. ^ Plants For A Future Database.
  17. ^ a b Plants of the Pacific Northwest Coast: Washington, Oregon, British Columbia & Alaska, Written by Paul Alaback, ISBN 978-1-55105-530-5
  18. ^ Erna Gunther. 1973. Ethnobotany of western Washington: The knowledge and use of indigenous plants by Native Americans.
  19. ^ Rutishauser, Rolf (1999): Polymerous Leaf Whorls in Vascular Plants: Developmental Morphology and Fuzziness of Organ Identities. International Journal of Plant Sciences 160(Supplement 6): 81–103. doi:10.1086/314221 PMID 10572024 PDF fulltext
  20. ^ Pigott, Anthony (4 October 2001). "Summary of Equisetum Taxonomy". National Collection of Equisetum. Archived from the original on 21 October 2010. Retrieved 17 June 2013. 
  21. ^ Fry, S. C.; Mohler, K. E.; Nesselrode, B. H. W. A.; Frankov, L. (2008). "Mixed-linkage -glucan:xyloglucan endotransglucosylase, a novel wall-remodelling enzyme fromEquisetum(horsetails) and charophytic algae". The Plant Journal 55 (2): 240–252. doi:10.1111/j.1365-313X.2008.03504.x. PMID 18397375.  edit
  22. ^ Fry, Stephen C.; Nesselrode, Bertram H. W. A.; Miller, Janice G.; Mewburn, Ben R. (2008). "Mixed-linkage (1→3,1→4)-β-d-glucan is a major hemicellulose of Equisetum (horsetail) cell walls". New Phytologist 179 (1): 104–15. doi:10.1111/j.1469-8137.2008.02435.x. PMID 18393951. 
  23. ^ Sørensen, Iben; Pettolino, Filomena A.; Wilson, Sarah M.; Doblin, Monika S.; Johansen, Bo; Bacic, Antony; Willats, William G. T. (2008). "Mixed-linkage (1→3),(1→4)-β-d-glucan is not unique to the Poales and is an abundant component of Equisetum arvense cell walls". The Plant Journal 54 (3): 510–21. doi:10.1111/j.1365-313X.2008.03453.x. PMID 18284587. 
  24. ^ "Horsetail". University of Maryland. Retrieved 2010-05-18. 
  25. ^ "Scientific opinion on the substantiation of health claims related to Equisetum arvense L. and invigoration of the body (ID 2437), maintenance of skin (ID 2438), maintenance of hair (ID 2438), maintenance of bone (ID 2439), and maintenance or achievement of a normal body weight (ID 2783) pursuant to Article 13 of Regulation (EC) No 1924/2006". European Food Safety Authority. Retrieved 2010-05-18. 
  26. ^ "Exploring Equisetum arvense L., Equisetum ramosissimum L. and Equisetum telmateia L. as sources of natural antioxidants". Phytotherapy Research - Ministry of Science and Environmental Protection of the Republic of Serbia via John Wiley & Sons. Retrieved 2010-05-18. "The ESR signal of DMPO-OH radical adducts in the presence of Equisetum telmateia phosphate buffer (pH 7) extract was reduced by 98.9% indicating that Equisetum telmateia could be a useful source of antioxidants with huge scavenging ability." 

Further reading[edit source | edit]

  • Walkowiak, Radoslaw (2008): IEAEquisetum Taxonomy. Version of 2008-10-04. Retrieved 2011-11-07.
  • Pryer, K.M.; Schuettpelz, E.; Wolf, P.G.; Schneider, H.; Smith, A.R. & Cranfill, R. (2004): Phylogeny and evolution of ferns (monilophytes) with a focus on the early leptosporangiate divergences. Am. J. Bot. 91(10): 1582-1598. PDF fulltext
  • Rutishauser, R. (1999). "Polymerous Leaf Whorls in Vascular Plants: Developmental Morphology and Fuzziness of Organ Identities". International Journal of Plant Sciences 160 (S6): S81–S103. doi:10.1086/314221. PMID 10572024.  edit
  • Weber, Reinhard (2005): Equisetites aequecaliginosus sp. nov., ein Riesenschachtelhalm aus der spättriassischen Formation Santa Clara, Sonora, Mexiko [Equisetites aequecaliginosus sp. nov., a tall horsetail from the Late Triassic Santa Clara Formation, Sonora, Mexico]. Revue de Paléobiologie 24(1): 331-364 [German with English abstract]. PDf fulltext
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