Etymology

The common names “field horsetail” and “common horsetail” both refer to the distinctive morphology of Equisetum species, which have jointed stems, whorls of needle-like branches, and highly reduced leaves. The name horsetail comes from the Latin Equisetum: equus or equip (horse) and seta or setum (tail, hair, bristle); in addition to a horse’s tail, this plant shares visual similarities with asparagus and bamboo (Carneiro et al. Reference Carneiro, Jardim, Araújo, Arantes, de Sousa, Barroso, Sousa, da Cunha, Cirilo and Bara2019; Filipov and Chiorescu, Reference Filipov and Chiorescu2021; Makia et al. Reference Makia, Al-Halbosiy and Al-Mashhadani2022; Şahinler Reference Şahinler2022; Villani Reference Villani2015). Another common name, “scouring rush” (also applied to E. hyemale L.), is associated with the presence of silicates, which give Equisetum species an abrasive texture that enables their use for cleaning kitchen implements and polishing wood (Burrill and Parker Reference Burrill and Parker1994; Filipov and Chiorescu, Reference Filipov and Chiorescu2021; Parrish et al. Reference Parrish, Lange, Šamec and Lange2022; Sapei Reference Sapei2007). Field horsetail belongs to the class Polypodiopsida, including pteridophytes such as ferns, quillworts, and club mosses, and the subclass Equisetidae, of which Equisetum species (sometimes controversially referred to as “living fossils”) are the only surviving members (Hrabovský and Zahradníková Reference Hrabovský and Zahradníková2022; Merryweather Reference Merryweather2020; Parrish et al. Reference Parrish, Lange, Šamec and Lange2022; Szypuła and Pietrosiuk Reference Szypuła and Pietrosiuk2021).

Distribution and Habitat

Field horsetail is native to many arctic and temperate areas of the northern hemisphere, including parts of Europe, North America, and Asia (Carneiro et al. Reference Carneiro, Tresvenzol, Jardim and Cunha2013; Parrish et al. Reference Parrish, Lange, Šamec and Lange2022; Paynter and Barton Reference Paynter and Barton2008; Sandhu et al. Reference Sandhu, Kaur and Chopra2010). The subclass Equisetidae is one of the oldest on earth, and continental movement is identified by Carneiro et al. (Reference Carneiro, Jardim, Araújo, Arantes, de Sousa, Barroso, Sousa, da Cunha, Cirilo and Bara2019) as a reason for the expansive native distribution of species within this group, including field horsetail, across the globe. In addition to its native distribution, field horsetail now occupies additional areas, including parts of the southern hemisphere (Figure 1; GBIF 2024). It was anthropogenically introduced to Mexico, South America, South Africa, and New Zealand (Hultén and Fries 1986 as cited by Svanberg Reference Svanberg1997). In Brazil, introduction was motivated by the potential medicinal properties of this plant, which is commonly referred to as “cavalinha”, from Portuguese cavalo (horse) and -inha (a suffix denoting smallness or shortness) (Almeida et al. Reference Almeida, Coheur and Candeias2015; Carneiro et al. Reference Carneiro, Jardim, Araújo, Arantes, de Sousa, Barroso, Sousa, da Cunha, Cirilo and Bara2019). Field horsetail is extremely problematic in New Zealand, where some populations cover areas up to 200 ha, and the National Pest Plant Accord lists the plant, along with all other Equisetum species, as invasive (Newfield and Champion Reference Newfield and Champion2010; Paynter and Barton Reference Paynter and Barton2008).

Figure 1. Global distribution of field horsetail, as reported between 2021 and 2024 (figure generated by GBIF 2024).

Field horsetail is prevalent in areas with moderate to high moisture levels, especially on well-drained soils, and can be found growing at elevations up to 1,100 to 1,500 m during summer months (Filipov and Chiorescu, Reference Filipov and Chiorescu2021; James and Rahman Reference James and Rahman2010; Makia et al. Reference Makia, Al-Halbosiy and Al-Mashhadani2022). Field horsetail is commonly found on coarse sandy soils but may also be found on dense clay soils (Labun et al. Reference Labun, Salamon and Grulova2012). Rhizomes and tubers contribute to abiotic stress tolerance as well as vegetative reproduction (Nakatani et al. Reference Nakatani, Noguchi and Kusanagi1993; Sakamaki and Ino Reference Sakamaki and Ino2006). This species tolerates a range of pH levels; however, it may be considered a bioindicator in acidic soils, as increased pH may be correlated with increased biomass (Bastiene et al. Reference Bastiene, Saulys and Ciuberkis2006; Filipov and Chiorescu, Reference Filipov and Chiorescu2021; Labun et al. Reference Labun, Salamon and Grulova2012). Once a stand is established, it may grow well in gravel roadways, riverbeds, and drier areas, with successful emergence even recorded in asphalt (Burrill and Parker Reference Burrill and Parker1994; Filipov and Chiorescu, Reference Filipov and Chiorescu2021; Heron et al. Reference Heron, Windham, Farrar and Pryer2021; James and Rahman Reference James and Rahman2010; Merryweather Reference Merryweather2020). Field horsetail is often prevalent in disturbed soils, such as fire-prone or agricultural areas (Holingswoth et al. Reference Holingswoth, Johnstone, Bernhardt and Chapin2013; Marshall Reference Marshall1986; Merryweather Reference Merryweather2020). Transport on farm machinery contributes to the spread of field horsetail within and between farms (Altland Reference Altland2005).

Biology and Ecology

Field horsetail is a vascular plant that produces and releases spores into the wind, which then germinate in damp soil (Burrill and Parker Reference Burrill and Parker1994; Bussmann et al. Reference Bussmann, Batsatsashvili and Kikvidze2020; Campbell Reference Campbell1883; Merryweather Reference Merryweather2020; Zhao et al. Reference Zhao, Gao, Suo, Chen, Wang and Dai2015). Fertile stems of field horsetail rapidly emerge between April and May and can be identified by their unbranched morphology and a tinge of red pigment (Burrill and Parker Reference Burrill and Parker1994; Campbell Reference Campbell1883; Carneiro et al. Reference Carneiro, Jardim, Araújo, Arantes, de Sousa, Barroso, Sousa, da Cunha, Cirilo and Bara2019; Parrish et al. Reference Parrish, Lange, Šamec and Lange2022; Yatskievych and Windham Reference Yatskievych and Windham2008). Fertile stems range from 10 to 25 cm in length, and the apex of each stalk produces a strobilus (sporangia-bearing cone) containing millions of viable spores, resembling green orbs, which are released prior to shoot demise (Figure 2; Bussmann et al. Reference Bussmann, Batsatsashvili and Kikvidze2020; Carneiro et al. Reference Carneiro, Jardim, Araújo, Arantes, de Sousa, Barroso, Sousa, da Cunha, Cirilo and Bara2019; Martinson et al. Reference Martinson, Hovda, Murphy and Weicherding2007; Merryweather Reference Merryweather2020; Yatskievych and Windham Reference Yatskievych and Windham2008). Under high humidity, the spores of Equisetum species can germinate within 2 d, which is advantageous because spores lose viability relatively quickly (Hoekstra Reference Hoekstra, Black and Pritchard2002; Zhao et al. Reference Zhao, Gao, Suo, Chen, Wang and Dai2015). Spores are enclosed in a tough case and can survive desiccation, with effective spring dispersal via floodwaters, mud, or birds (Edwards et al. Reference Edwards, Laskowski, Baskin, Mitchell and DeMeo2019; Hoekstra Reference Hoekstra, Black and Pritchard2002; Parker Reference Parker2009; Yatskievych and Windham Reference Yatskievych and Windham2008). Fertile stems of field horsetail are less common than and precede emergence of sterile vegetative stems, which may reach 50 cm in length (Burrill and Parker Reference Burrill and Parker1994; Merryweather Reference Merryweather2020). The vegetative stems are green and photosynthetic, although leaves remain highly reduced with a singular unbranched vein (microphylls) (Figure 3; Carneiro et al. Reference Carneiro, Jardim, Araújo, Arantes, de Sousa, Barroso, Sousa, da Cunha, Cirilo and Bara2019; Makia et al. Reference Makia, Al-Halbosiy and Al-Mashhadani2022).

Figure 2. Fertile stems of field horsetail showing strobuli (sporangia-bearing cones). Photo credit: Joseph Neal.

Figure 3. Vegetative stems of field horsetail. Photo credit: Randy Prostak.

Plants tend to develop aboveground photosynthetic structures and then transport photosynthate to rhizomes and tubers, which account for 85% of the plants’ annual dry-mass production (Sakamaki and Ino Reference Sakamaki and Ino2006; Sandstedt Reference Sandstedt2011). These underground structures form thick mats that can grow up to several meters deep in soil, act as storage organs, and enable vegetative reproduction (James and Rahman Reference James and Rahman2010; Sakamaki and Ino Reference Sakamaki and Ino2006). Rhizome fragments contain lower starch content than tubers but offer greater rates of regrowth (Sakamaki and Ino Reference Sakamaki and Ino2006).

Field horsetail exhibits sensitivity to light, water, and crop competition (Andersson and Lundegårdh Reference Andersson and Lundegårdh1999a; Cloutier and Watson Reference Cloutier and Watson1985). Shaded conditions require plants to rely on starch reserves in rhizomes and tubers (Andersson and Lundegårdh Reference Andersson and Lundegårdh1999b; Sakamaki and Ino Reference Sakamaki and Ino2006). Response to nitrogen application is minimal in field horsetail, so more nitrogen-responsive plants may have a competitive advantage under fertilized field conditions (Andersson and Lundegårdh Reference Andersson and Lundegårdh1999a; Harbur and Owen Reference Harbur and Owen2004). Field horsetail has high demands for potassium, which increases tolerance of environmental stresses such as drought, high temperature, cold weather, and disease (Andersson and Lundegårdh Reference Andersson and Lundegårdh1999b; Hasanuzzaman et al. Reference Hasanuzzaman, Bhuyan, Nahar, Hossain, Mahmud, Hossen, Masud and Moumita2018; Kafkafi Reference Kafkafi1990; Labun et al. Reference Labun, Salamon and Grulova2012). Field horsetail is sensitive to water stress, and competition for water can contribute to mortality (Cloutier and Watson Reference Cloutier and Watson1985).

Weediness

Field horsetail is recognized as a challenging agricultural weed worldwide (Figure 4; Bastiene et al. Reference Bastiene, Saulys and Ciuberkis2006; Liew et al. Reference Liew, Andersson, Boström, Forkman, Hakman and Magnuski2013). Perennial weed species, including field horsetail, are most problematic in reduced tillage and no-tillage cropping systems (Légère and Samson Reference Légère and Samson2004; Nakatani et al. Reference Nakatani, Noguchi and Kusanagi1993; Sims et al. Reference Sims, Corsi, Gbehounou, Kienzle, Taguchi and Friedrich2018). Conservation tillage in spring improved field horsetail control and crop yield, relative to no-till crop production (Arshad et al. Reference Arshad, Gill and Coy1994). Although field horsetail is most prevalent in no-till areas, it can even be problematic in tilled agricultural fields. In fields with root-restricting hard or plow pans, reduced access to water and nutrients impedes cash crop growth; however, field horsetail rhizomes can extend into cracks in plow pans to enable continued survival and spread (Elkins et al. Reference Elkins, Thurlow and Hendrick1983; Filipov and Chiorescu Reference Filipov and Chiorescu2021; Suleymanov et al. Reference Suleymanov, Yaparov, Saifullin, Vildanov, Shirokikh, Suleymanov, Komissarov, Liebelt, Nigmatullin and Khamidullin2020; Witt and Haefele Reference Witt and Haefele2005).

Figure 4. Field horsetail infesting summer squash. Photo credit: Joseph DiTomaso.

A field horsetail shoot density of 280 shoots m^–2 reduced corn yield by over 40%, but yield loss was not observed when the weed occurred at a lower density of 180 shoots m^–2 or was removed within 5 to 8 wk after corn emergence (Cloutier Reference Cloutier1982). Specialty crops such as strawberries or ornamentals may be so highly infested with field horsetail that the crop is lost (Peabody and Roche Reference Peabody and Roche1963). In addition to competing for moisture and nutrients, field horsetail can penetrate tile drainage systems and obstruct irrigation for crops (Bastiene et al. Reference Bastiene, Saulys and Ciuberkis2006; Kladivko and Brown Reference Kladivko and Brown2016). In Lithuania, obstruction of drainage systems in agricultural fields by dense root systems of field horsetail accounts for one third of all drainage failures (Bastiene et al. Reference Bastiene, Saulys and Ciuberkis2006).

Field horsetail is problematic in grazing systems and can be toxic to livestock, especially horses (Burrill and Parker Reference Burrill and Parker1994). Poisoning of livestock by field horsetail is known as “equisetosis” (Dayton Reference Dayton1960; Pammel Reference Pammel1911; Peabody and Roche Reference Peabody and Roche1963; Steyn Reference Steyn1933). In horses, this plant’s thiaminase enzyme induces vitamin B₁ deficiency, leading to symptoms including wobbly gait, weakness, slow pulse, fever, depression, nervousness, and sometimes even mortality (Bates Reference Bates2023; Burrill and Parker Reference Burrill and Parker1994; Martinson et al. Reference Martinson, Hovda, Murphy and Weicherding2007; Pammel Reference Pammel1911; Pohl Reference Pohl1955; Rapp Reference Rapp1954). Field horsetail is most likely to be dangerous if it is consumed dry in hay rather than fresh as forage and comprises at least 5% of total hay volume (Ingebrigtsen Reference Ingebrigtsen2010; Peabody and Roche Reference Peabody and Roche1963; Rapp Reference Rapp1954).

Other ruminant animals affected by consumption of field horsetail include cows and sheep, though symptoms are seen at decreased rates in both animals compared with horses (Burrill and Parker Reference Burrill and Parker1994; Pammel Reference Pammel1911; Paynter and Barton Reference Paynter and Barton2008; Rapp Reference Rapp1954; Svanberg Reference Svanberg1997). The high levels of silica in field horsetail reduce its desirability as forage for cows, which may exhibit diarrhea, weight loss, and spoiled milk with decreased production after ingesting field horsetail (Bell and Popay Reference Bell and Popay1988; El Mahdy et al. Reference El Mahdy, Popescu and Borda2017; Rapp Reference Rapp1954). Especially in calves, severe symptoms may include cardiac or respiratory issues and even convulsions (El Mahdy et al. Reference El Mahdy, Popescu and Borda2017 and references therein). Sheep who are pregnant and consume field horsetail may be susceptible to premature delivery (Svanberg Reference Svanberg1997 and references therein). For these reasons, it is advisable to control field horsetail in pastures (Riet-Correa et al. Reference Riet-Correa, Medeiros, Pfister and Mendonça2017).

Field horsetail can also be problematic in non-agricultural contexts. It has been a major issue along railway tracks in Sweden, because glyphosate, commonly used for weed control along tracks, does not provide complete control of this species (Torstensson Reference Torstensson2001; Torstensson and Börjesson Reference Torstensson and Börjesson2004).

Chemical Control

Chemical control of field horsetail can be difficult, and reported outcomes from previous experiments have been mixed (Table 1). Challenges in controlling this species with herbicides largely reflect poor retention or translocation (Marshall Reference Marshall1984). In British Columbia, Canada, application of amitrole at 9 kg ha^–1 between July 16 and July 30 reduced field horsetail stand population by 96% after 1 yr (Hoyt and Carder Reference Hoyt and Carder1962). In the same study, MCPA applied at 0.3 to 0.6 kg ha^–1 reduced stand population the next year by 50% to 65% (Hoyt and Carder Reference Hoyt and Carder1962). Bell and Popay (Reference Bell and Popay1988) found that amitrole (4.4 kg ai ha^–1), glyphosate (1.0 or 2.0 kg ai ha^–1), dichlobenil (11 kg ai ha^–1), picloram (0.25 or 0.5 kg ai ha^–1), and 2,4-D + picloram (0.5 + 0.125 or 1.0 + 0.25 kg ai ha^–1) did not achieve sustained control. Undiluted glyphosate (360 g ai L^–1) (sponge application) reduced stem density the year after application (Ainsworth et al. Reference Ainsworth, Gunasekera and Bonilla2006). MCPA (500 g ai L^–1) at 4.5 ml L^–1 (spray application) prevented growth the year after application (Ainsworth et al. Reference Ainsworth, Gunasekera and Bonilla2006).

Table 1. Examples of herbicide treatments that have been tested on field horsetail

In greenhouse trials, imazapyr (0.125% ai), amitrole (1.8% or 3.6% ai), metsulfuron (0.03% ai), and picloram (0.02 or 0.04 g pot^–1) achieved good aboveground control (James and Rahman Reference James and Rahman2010). In field trials of the same study, field horsetail exhibited regrowth following treatments of amitrole (3.6% ai), metsulfuron (0.03% ai), and MCPA (0.16% ai) within 2 mo after treatment (James and Rahman Reference James and Rahman2010). Triazine has also been reported to be ineffective at controlling field horsetail (Rola and Pejka Reference Rola and Pejka1970; Šarić et al. Reference Šarić, Ostojić, Stefanović, Milanova, Kazinczi and Tyšer2011). In British Columbia, Canada, Bae et al. (Reference Bae, Young, Elsby and Critchley2022) tested herbicide application times aligned with cranberry phenology. Applications of dichlobenil (4,400 g ai ha^–1) post-harvest, clopyralid (102 g ai ha^–1) or mesotrione (100.8 g ai ha^–1) at bud break, and mesotrione (100.8 g ai ha^–1) + sethoxydim (495 g ai ha^–1) at the hook stage allowed for >90% control of field horsetail 56 d after the final treatment (Bae et al. Reference Bae, Young, Elsby and Critchley2022).

In trials conducted within corn fields of Ontario, Canada, postemergence applications of flumetsulam + MCPA amine (50 + 630 g ai ha^–1) reduced field horsetail biomass by 82% and density by 75% (Soltani et al. Reference Soltani, McNaughton and Sikkema2015). Biomass and density were reduced by 87% and 78%, respectively, by postemergence application of nicosulfuron/rimsulfuron + flumetsulam + MCPA amine (25 + 50 + 630 g ai ha^–1). This treatment provided 70% to 83% visual weed control (Soltani et al. Reference Soltani, McNaughton and Sikkema2015).

Dichlobenil is an example of an herbicide that reduces stand populations but, when applied alone, cannot fully destroy underground rhizome and tuber structures (Bell and Popay Reference Bell and Popay1988; Marshall Reference Marshall1984; Ryan Reference Ryan1976). Miller et al. (Reference Miller, Libbey and Maupin2012) found that practices such as flame application (causing defoliation), hand hoeing, and especially dormant-season application of dichlobenil helped control field horsetail. These findings are consistent with general guidance suggesting that nonchemical and chemical control methods may be combined for effective weed control (Bastiene et al. Reference Bastiene, Saulys and Ciuberkis2006; Koning et al. Reference Koning, de Mol and Gerowitt2019).

Mechanical Control

Early-season defoliation can be an effective tactic in conservation tillage systems, because this approach hampers the plant’s ability to restore its belowground reserves (Bostrom et al. Reference Bostrom, Andersson, Forkman, Hakman, Liew and Magnuski2013; Liew et al. Reference Liew, Andersson, Boström, Forkman, Hakman and Magnuski2013). Mowing provides some control but does not necessarily result in mortality because of the belowground reserves (Ainsworth et al. Reference Ainsworth, Gunasekera and Bonilla2006; Conn and Delapp Reference Conn and Delapp1983). Deep excavation is possible at small scales, but the expense of equipment makes this approach cost-prohibitive at larger scales (Ainsworth et al. Reference Ainsworth, Gunasekera and Bonilla2006). It is also important to note that fragmentation of rhizomes can facilitate the spread of field horsetail (Sakamaki and Ino Reference Sakamaki and Ino2006). Mechanical control was found to be 32% more effective for perennial weeds including field horsetail, relative to thermal weed control (Virbickaite et al. Reference Virbickaite, Sirvydas, Kerpauskas and Vasinauskiene2006). In a study conducted by Archut et al. (Reference Archut, Jendrny, Schulte-Marxloh, Eberius, Conrath and Schindler2023), field horsetail showed low regrowth rates along makeshift railway tracks after 41 d of hot-water application (95 to 98 C) at 10 L m^–2 and 20 L m^–2 from a height of 20 cm.

Koning et al. (Reference Koning, de Mol and Gerowitt2019) compared effects of glyphosate application and tillage on weeds including field horsetail. Treatments included (i) glyphosate at 100% of the recommended rate (1,080 g ai ha^–1), (ii) glyphosate at 50% of the recommended rate (540 g ai ha^–1), (iii) chisel plowing, and (iv) moldboard plowing (Koning et al. Reference Koning, de Mol and Gerowitt2019). Each treatment was applied two or three times within the season. This experiment demonstrated decreased abundance of field horsetail and other creeping perennials in glyphosate treatments compared with tilled treatments (Koning et al. Reference Koning, de Mol and Gerowitt2019). Forget-me-not [Myosotis arvensis (L.) Hill] and common poppy (Papaver rhoeas L.), were among the species more abundant in glyphosate treatments, with tolerance attributed to reduced foliar uptake of the herbicide (Koning et al. Reference Koning, de Mol and Gerowitt2019).

Current and Potential Uses

Field horsetail is pharmacologically active and can be used in numerous ways. It has been incorporated into traditional medicines and consumed as food throughout history (Luanda et al. Reference Luanda, Ripanda and Makangara2023; Svanberg Reference Svanberg1997), typically as tea or other oral preparations (Kultur et al. Reference Kultur, Gurdal, Sari and Melikoglu2021). Galatian peoples historically used the plant to dye fabrics, and Romans consumed it as a vitamin C supplement (Svanberg Reference Svanberg1997; Villani Reference Villani2015). Extensive research on this plant has suggested anticancer, antitumor, anti-inflammatory, antibacterial, antifungal, and antidiabetic benefits (Al Mohammed et al. Reference Al Mohammed, Paray and Rather2017; Luanda et al. Reference Luanda, Ripanda and Makangara2023; Taylor et al. Reference Taylor, Bonafos, Chovelon, Parvaud, Furet, Aveline and Marchand2022). It may also help treat respiratory, urinary, digestive, and inflammatory disorders (Kultur et al. Reference Kultur, Gurdal, Sari and Melikoglu2021; Luanda et al. Reference Luanda, Ripanda and Makangara2023). Ointment containing field horsetail was found to encourage wound healing after episiotomies in a randomized placebo trial (Asgharikhatooni et al. Reference Asgharikhatooni, Bani, Hasanpoor, Alizade and Javadzadeh2015). Horsetail extracts may contribute to bone regeneration in individuals with osteoporosis and arthritis (da Costa e Silva et al. Reference da Costa e Silva, Alves Diniz, da Fonte Ferreira and Murthy2022; Labun et al. Reference Labun, Grulova, Salamon and Serseň2013). A diet including 60 mg kg^–1 of field horsetail extract increased trabecular bone thickness in rats by 11% to 46% (da Costa e Silva et al. Reference da Costa e Silva, Alves Diniz, da Fonte Ferreira and Murthy2022). In addition, in vitro studies suggested that field horsetail, used in combination with palmitoylethanolamide, can help alleviate neuropathic pain by acting on the peripheral nervous system (Ruga et al. Reference Ruga, Galla, Ferrari, Invernizzi and Uberti2023).

A literature review found that, although data are available on the efficacy of field horsetail–based products, these products do not meet safety criteria for medicinal applications (Carneiro et al. Reference Carneiro, Tresvenzol, Jardim and Cunha2013). The review acknowledged the ancient and traditional uses of field horsetail in medicine and encouraged continued research efforts on their potential future applications (Carneiro et al. Reference Carneiro, Tresvenzol, Jardim and Cunha2013, Reference Carneiro, Jardim, Araújo, Arantes, de Sousa, Barroso, Sousa, da Cunha, Cirilo and Bara2019).