''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Equisetaceae Equisetaceae, sometimes called the horsetail family, is the only extant family of the order Equisetales, with one surviving genus, ''Equisetum'', which comprises about twenty species. Evolution and systematics Equisetaceae is the only survivin ...

, a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

ferns A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except th ...

, which reproduce by

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

s rather than seeds. ''Equisetum'' is a "

living fossil A living fossil is an extant taxon that cosmetically resembles related species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living fossi ...

", the only living genus of the entire subclass

Equisetidae Equisetidae is one of the four subclasses of Polypodiopsida (ferns), a group of vascular plants with a fossil record going back to the Devonian. They are commonly known as horsetails. They typically grow in wet areas, with whorls of needle-like ...

, which for over 100 million years was much more diverse and dominated the

understorey In forestry and ecology, understory (American English), or understorey (Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the forest canopy without penetrating it to any great extent, but abov ...

of late

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

forests. Some equisetids were large

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

s reaching to tall. The genus ''

Calamites ''Calamites'' is a genus of extinct arborescent (tree-like) horsetails to which the modern horsetails (genus ''Equisetum'') are closely related. Unlike their herbaceous modern cousins, these plants were medium-sized trees, growing to heights o ...

'' of the family

Calamitaceae Calamitaceae is an extinct family of plants related to the modern horsetails. Some members of this family attained tree-like stature during the Carboniferous Period (around ) and in Permian Period, reaching heights of up to 20 meters. The famil ...

, for example, is abundant in

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

deposits from the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

period. The pattern of spacing of nodes in horsetails, wherein those toward the apex of the shoot are increasingly close together, is said to have inspired

John Napier John Napier of Merchiston (; 1 February 1550 – 4 April 1617), nicknamed Marvellous Merchiston, was a Scottish landowner known as a mathematician, physicist, and astronomer. He was the 8th Laird of Merchiston. His Latinized name was Ioann ...

to invent

logarithm In mathematics, the logarithm is the inverse function to exponentiation. That means the logarithm of a number to the base is the exponent to which must be raised, to produce . For example, since , the ''logarithm base'' 10 o ...

s. Modern horsetails first appeared during the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

period. A superficially similar but entirely unrelated

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

genus, mare's tail (''

Hippuris ''Hippuris'', the mare's tail, was previously the sole genus in the family Hippuridaceae. Following genetic research by the Angiosperm Phylogeny Group, it has now been transferred to the family Plantaginaceae, with Hippuridaceae being reduced to ...

''), is occasionally referred to as "horsetail", and adding to confusion, the name "mare's tail" is sometimes applied to ''Equisetum''. Despite centuries of use in

traditional medicine Traditional medicine (also known as indigenous medicine or folk medicine) comprises medical aspects of traditional knowledge that developed over generations within the folk beliefs of various societies, including indigenous peoples, before the ...

, there is no evidence that ''Equisetum'' has any medicinal properties.

Etymology

The name "horsetail", often used for the entire group, arose because the branched species somewhat resemble a

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million y ...

's tail. Similarly, the

scientific name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''Equisetum'' is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

('horse') + ('bristle'). Other names include candock for branching species, and snake grass or scouring-rush for unbranched or sparsely branched species. The latter name refers to the rush-like appearance of the plants and to the fact that the stems are coated with abrasive

silicate In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is al ...

s, making them useful for scouring (cleaning) metal items such as cooking pots or drinking mugs, particularly those made of

tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...

. '' E. hyemale'', rough horsetail, is still boiled and then dried in

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

to be used for the final polishing process on

woodcraft The term woodcraft — or woodlore — denotes bushcraft skills and experience in matters relating to living and thriving in the woods—such as hunting, fishing, and camping—whether on a short- or long-term basis. Traditionally, woodcraft per ...

to produce a smooth finish. In

German German(s) may refer to: * Germany (of or related to) ** Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...

, the corresponding name is ('tin-herb'). In

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...

-speaking countries, these plants are known as ('horsetail').

Description

''Equisetum''

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

are greatly reduced and usually non-

photosynthetic Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...

. They contain a single, non-branching vascular trace, which is the defining feature of

microphyll In plant anatomy and evolution a microphyll (or lycophyll) is a type of plant leaf with one single, unbranched leaf vein. Plants with microphyll leaves occur early in the fossil record, and few such plants exist today. In the classical concept of ...

s. However, it has recently been recognised that horsetail microphylls are probably not ancestral as in

lycophyte The lycophytes, when broadly circumscribed, are a vascular plant (tracheophyte) subgroup of the kingdom Plantae. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldes ...

s (clubmosses and relatives), but rather derived

adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...

s, evolved by reduction of

megaphylls A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

. The leaves of horsetails are arranged in

whorls A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). Whorls in nature File:Photograph and axial plane floral ...

fused into

nodal Nodal homolog is a secretory protein that in humans is encoded by the ''NODAL'' gene which is located on chromosome 10q22.1. It belongs to the transforming growth factor beta superfamily (TGF-β superfamily). Like many other members of this superf ...

sheaths. The stems are usually 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. Unusually, the branches often emerge below the leaves in an internode, and grow from buds between their bases.

Spores

The

s are borne under sporangiophores in

strobili A strobilus (plural: strobili) is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem. Strobili are often called cones, but some botanists restrict the use of the term cone to th ...

, 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. '' E. arvense'', field horsetail) they are non-photosynthetic, produced early in spring. In some other species (e.g. '' E. palustre'', marsh horsetail) they are very similar to sterile shoots, photosynthetic and with whorls of branches. Horsetails are mostly

homosporous In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

, though in the field horsetail, smaller spores give rise to male

prothalli A prothallus, or prothallium, (from Latin ''pro'' = forwards and Greek ''θαλλος'' (''thallos'') = twig) is usually the gametophyte stage in the life of a fern or other pteridophyte. Occasionally the term is also used to describe the young ...

. The spores have four

elater An elater is a cell (or structure attached to a cell) that is hygroscopic, and therefore will change shape in response to changes in moisture in the environment. Elaters come in a variety of forms, but are always associated with plant spores. In ...

s that act as moisture-sensitive springs, assisting spore dispersal through crawling and hopping motions after the

sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

have split open longitudinally.

''Equisetum'' cell walls

The crude cell extracts of all ''Equisetum'' species tested contain mixed-linkage glucan : Xyloglucan endotransglucosylase (MXE) activity. 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 Mixed-linkage glucan (MLG), sometimes incorrectly referred to as beta-glucan, is a hemicellulosic polysaccharide consisting of β-D(1-3) and β-D(1-4) linked glucosyl residues. MLG is highly prevalent within the Poales, where it has important prop ...

(MLG), a

polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...

which, until recently, was thought to be confined to the

Poales The Poales are a large order of flowering plants in the monocotyledons, and includes families of plants such as the grasses, bromeliads, and sedges. Sixteen plant families are currently recognized by botanists to be part of Poales. Descriptio ...

. 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. Non-''Equisetum'' land plants tested lack detectable MXE activity. An observed negative correlation between XET activity and cell age led to the suggestion that XET may be catalysing endotransglycosylation in controlled wall-loosening during cell expansion. 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.

Taxonomy

Species

The living members of the genus ''Equisetum'' are divided into three distinct lineages, which are usually treated as

subgenera In biology, a subgenus (plural: subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between t ...

. The name of the type subgenus, ''Equisetum'', means "horse hair" in

, while the name of the other large subgenus, ''Hippochaete'', means "horse hair" in

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

Hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two dif ...

s are common, but hybridization has only been recorded between members of the same subgenus. While plants of subgenus ''Equisetum'' are usually referred to as horsetails, those of subgenus ''Hippochaete'' are often called scouring rushes, especially when unbranched. Two ''Equisetum'' plants are sold commercially under the names ''Equisetum japonicum'' (barred horsetail) and ''Equisetum camtschatcense'' (Kamchatka horsetail). These are both types of ''E. hyemale'' var. ''hyemale'', although they may also be listed as separate varieties of ''E. hyemale''.

Evolutionary history

The oldest remains of modern horsetails of the genus ''Equisetum'' first appear in the Early Jurassic, represented by '' Equisetum dimorphum'' from the Early Jurassic of Patagonia and ''

Equisetum laterale ''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass E ...

'' from the Early-Middle Jurassic of Australia.

Silicified In geology, petrifaction or petrification () is the process by which organic material becomes a fossil through the replacement of the original material and the filling of the original pore spaces with minerals. Petrified wood typifies this proce ...

remains of ''

Equisetum thermale ''Equisetum thermale'' is an extinct horsetail species in the family Equisetaceae described from a group of whole plant fossils including rhizomes, stems, and leaves. The species is known from Middle to Late Jurassic sediments exposed in the p ...

'' from the Late Jurassic of Argentina exhibit all the morphological characters of modern members of the genus. The estimated split between ''

Equisetum bogotense ''Equisetum bogotense'', the Andean horsetail, is a herbaceous perennial that reproduces through spores. It has thicker less bushy whorled branches, and a silica rich rhizomatous stem, which roots grow out of, under ground. This stem is a dull ...

'' and all other living ''Equisetum'' is estimated to have occurred no later than the Early Jurassic.

Subgenus ''Paramochaete''

* – Andean horsetail; upland

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

up to

Costa Rica Costa Rica (, ; ; literally "Rich Coast"), officially the Republic of Costa Rica ( es, República de Costa Rica), is a country in the Central American region of North America, bordered by Nicaragua to the north, the Caribbean Sea to the no ...

; includes ''E. rinihuense'', sometimes treated as a separate species. Previously included in subg. ''Equisetum'', but Christenhusz ''et al.'' (2019) transfer this here, as ''E. bogotense'' appears to be sister to the remaining species in the genus.

Subgenus ''Equisetum''

* – field horsetail, common horsetail or mare's tail; circumboreal down through temperate zones * – Himalayan horsetail; Himalayan India and China and adjacent nations above about 1500 feet (450 m) * – water horsetail; circumboreal down through temperate zones * – marsh horsetail; circumboreal down through temperate zones * – meadow horsetail, shade horsetail, shady horsetail; circumboreal except for tundra down through cool temperate zones * – wood horsetail; circumboreal down through cool temperate zones, more restricted in east Asia * – great horsetail, northern giant horsetail; Europe to Asia Minor and north Africa, also west coast of North America. The North American subspecies may be treated as a separate species

Subgenus ''Hippochaete''

* – southern giant horsetail or giant horsetail; temperate to tropical South America and Central America north to southern Mexico * – rough horsetail, rough scouring rush; most of non-tropical northern hemisphere. The North American subspecies may be treated as a separate species * – smooth horsetail, smooth scouring rush; western 3/4 of North America down into northwestern Mexico; also sometimes known as ''Equisetum kansanum'' * – Mexican giant horsetail; from central Mexico south to Peru * (including '' E. debile'') – branched horsetail; Asia, Europe, Africa, southwest Pacific islands * – dwarf horsetail, dwarf scouring rush; northern (cool temperate) zones worldwide * – variegated horsetail, variegated scouring rush; northern (cool temperate) zones worldwide, except for northeasternmost Asia

Unplaced to subgenus

*'' Equisetum dimorphum'' –

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...

, Argentina *''

–'' Early to

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

, Australia *''

'' – Middle to

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

, Argentina *'' Equisetum similkamense'' -

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

, British Columbia

Named hybrids

Hybrids between species in subgenus ''Equisetum''

* ''Equisetum'' × ''bowmanii'' (''Equisetum sylvaticum'' × ''Equisetum telmateia'') * ''Equisetum'' × ''dycei'' (''Equisetum fluviatile'' × ''Equisetum palustre'') * ''Equisetum'' × ''font-queri'' (''Equisetum palustre'' × ''Equisetum telmateia'') * ''Equisetum'' × ''litorale'' (''Equisetum arvense'' × ''Equisetum fluviatile'') * ''Equisetum'' × ''mchaffieae'' (''Equisetum fluviatile'' × ''Equisetum pratense'') * ''Equisetum'' × ''mildeanum'' (''Equisetum pratense'' × ''Equisetum sylvaticum'') * ''Equisetum'' × ''robertsii'' (''Equisetum arvense'' × ''Equisetum telmateia'') * ''Equisetum'' × ''rothmaleri'' (''Equisetum arvense'' × ''Equisetum palustre'') * ''Equisetum'' × ''willmotii'' (''Equisetum fluviatile'' × ''Equisetum telmateia'')

Hybrids between species in subgenus ''Hippochaete''

* ''Equisetum'' × ''ferrissii'' (''Equisetum hyemale'' × ''Equisetum laevigatum'') * ''Equisetum'' × ''moorei'' (''Equisetum hyemale'' × ''Equisetum ramosissimum'') * ''Equisetum'' × ''nelsonii'' (''Equisetum laevigatum'' × ''Equisetum variegatum'') * ''Equisetum'' × ''schaffneri'' (''Equisetum giganteum'' × ''Equisetum myriochaetum'') * ''Equisetum'' × ''trachyodon'' (''Equisetum hyemale'' × ''Equisetum variegatum'')

Phylogeny

Distribution and ecology

The genus ''Equisetum'' as a whole, while concentrated in the non-tropical northern hemisphere, is near-

cosmopolitan Cosmopolitan may refer to: Food and drink * Cosmopolitan (cocktail), also known as a "Cosmo" History * Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953 Hotels and resorts * Cosmopoli ...

, being absent only from

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

, though they are not known to be native to Australia, New Zealand nor the islands of the Pacific. They are most common in northern North America (Canada and the northernmost United States), where the genus is represented by nine species (''E. arvense'', ''E. fluviatile'', ''E. hyemale'', ''E. laevigatum'', ''E. palustre'', ''E. pratense'', ''E. scirpoides'', ''E. sylvaticum, and ''E. variegatum''). Only four (''E. bogotense'', ''E. giganteum'', ''E. myriochaetum'', and ''E. ramosissimum'') of the fifteen species are known to be native south of the Equator. They are

perennial plant A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...

and dying back in winter as most temperate species, or

evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which ...

as most tropical species and the temperate species '' E. hyemale'' (rough horsetail), '' E. ramosissimum'' (branched horsetail), '' E. scirpoides'' (dwarf horsetail) and '' E. variegatum'' (variegated horsetail). They typically grow 20 cm–1.5 m (8 in–5 ft) tall, though the "giant horsetails" are recorded to grow as high as ('' E. telmateia'', northern giant horsetail), ('' E. giganteum'', southern giant horsetail) or ('' E. myriochaetum'', Mexican giant horsetail), and allegedly even more. One species, ''

Equisetum fluviatile ''Equisetum fluviatile'', the water horsetail or swamp horsetail, is a vascular plant that commonly grows in dense colonies along freshwater shorelines or in shallow water in ponds, swamps, ditches, and other sluggish or still waters with mud bo ...

'', is an emergent aquatic, rooted in water with shoots growing into the air. The stalks arise from

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

s that are deep underground and difficult to dig out. Field horsetail ('' E. arvense'') can be a nuisance

weed A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...

, readily regrowing from the rhizome after being pulled out. It is unaffected by many

herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

s designed to kill

seed plants A spermatophyte (; ), also known as phanerogam (taxon Phanerogamae) or phaenogam (taxon Phaenogamae), is any plant that produces seeds, hence the alternative name seed plant. Spermatophytes are a subset of the embryophytes or land plants. They inc ...

. Since the stems have a waxy coat, the plant is resistant to contact weedkillers like glyphosate. However, as ''E. arvense'' prefers an acid soil,

lime Lime commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Botany ...

may be used to assist in eradication efforts to bring the

soil pH Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...

to 7 or 8. Members of the genus have been declared noxious weeds in

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

and in the US state of

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

. All the ''Equisetum'' are classed as "unwanted organisms" in

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

and are listed on the

National Pest Plant Accord The National Pest Plant Accord (NPPA) is a New Zealand agreement that identifies pest plants that are prohibited from sale and commercial propagation and distribution. The Accord initially came into effect on 1 October 2001 between regional coun ...

Consumption

People have regularly consumed horsetails. For example, the fertile stems bearing strobili of some species are cooked and eaten like asparagus (a dish called in

). Native Americans in the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...

eat the young shoots of this plant raw. The young plants are eaten cooked or raw, but considerable care must be taken. If eaten over a long enough period of time, some species of horsetail can be

poison Poison is a chemical substance that has a detrimental effect to life. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broa ...

ous to grazing animals, including

horses The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

. The toxicity appears to be due to

thiaminase Thiaminase is an enzyme that metabolizes or breaks down thiamine into two molecular parts. It is an antinutrient when consumed. The old name was "aneurinase". There are two types: * Thiamine pyridinylase, Thiaminase I (, ) * Aminopyrimidine am ...

, which can cause thiamin (vitamin B1) deficiency. ''Equisetum'' species may have been a common food for herbivorous dinosaurs. With studies showing silicate within

hadrosaur Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which includ ...

teeth and that horsetails are nutritionally of high quality, it is assumed that horsetails were an important component of herbivorous dinosaur diets.

Folk medicine and safety concerns

Extracts and other preparations of ''E. arvense'' have served as

herbal remedies Herbal medicine (also herbalism) is the study of pharmacognosy and the use of medicinal plants, which are a basis of traditional medicine. With worldwide research into pharmacology, some herbal medicines have been translated into modern remedie ...

, with records dating over centuries. In 2009, the

European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002, ...

concluded there was no evidence for the supposed

health effects Health effects (or health impacts) are changes in health resulting from exposure to a source. Health effects are an important consideration in many areas, such as hygiene, pollution studies, occupational safety and health, ( utrition and health sc ...

of ''E. arvense'', such as for invigoration, weight control, skincare, hair health or bone health. , there is insufficient scientific evidence for its effectiveness as a medicine to treat any human condition. ''E. arvense'' contains

, which metabolizes the

B vitamin B vitamins are a class of water-soluble vitamins that play important roles in Cell (biology), cell metabolism and synthesis of red blood cells. Though these vitamins share similar names (B1, B2, B3, etc.), they are chemically distinct compounds th ...

thiamine Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient, that cannot be made in the body. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thi ...

, potentially causing

thiamine deficiency Thiamine deficiency is a medical condition of low levels of thiamine (Vitamin B1). A severe and chronic form is known as beriberi. The two main types in adults are wet beriberi and dry beriberi. Wet beriberi affects the cardiovascular system, r ...

and associated

liver damage Liver disease, or hepatic disease, is any of many diseases of the liver. If long-lasting it is termed chronic liver disease. Although the diseases differ in detail, liver diseases often have features in common. Signs and symptoms Some of the si ...

, if taken chronically. Horsetail might produce a diuretic effect. Further, its safety for oral consumption has not been sufficiently evaluated and it may be

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...

, especially to children and pregnant women.

References

External links

''Equisetum''
at the Tree of Life Web Project
National Collection of ''Equisetum''

International Equisetological Association
* {{Authority control Fern genera Medicinal plants Extant Middle Jurassic first appearances Callovian first appearances Callovian genus first appearances Taxa named by Carl Linnaeus