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Equisetum hyemale L., Rough Horsetail

Account Summary

Native, rare, but occasionally locally abundant. Circumpolar boreo-temperate.

1872; Smith, T.O.; Colebrooke River (unspecified region).

March to December.

Growth form and preferred habitats

This rare, slow-growing, rhizomatous, evergreen horsetail species, with its distinctive rough texture, is regularly found growing on shady, sloping river banks and streamsides, which represent its predominant habitat throughout Britain & Ireland. It typically grows in heavy, permanently moist, sandy or clayey soils that are rich in silica and other minerals. It can also be found in base-rich moorland flushes, and elsewhere in similar flushes on sand dunes (C. Dixon & T.D. Dines In: Preston et al. 2002).

Identification

The erect, unbranched, dark blue-green stems are pencil-thick and the ash-white, toothless sheaths with black bands around the top and bottom make E. hyemale reasonably easy to distinguish from its hybrid with E. variegatum, E. × trachyodon. When the leaf sheaths are young they do appear to bear short teeth. In reality, these are minute scallops where the true sheath teeth would normally be attached (Page 1997, p. 450), but they are not observable on mature sheaths (Rose 1989). In the current author's experience, E. hyemale and E. × trachyodon only rarely associate with one another.

Fermanagh occurrence

This distinctive horsetail has been recorded in Fermanagh from 14 thinly scattered tetrads, 2.7% of those in the VC. Twelve tetrads have post-1975 records in habitats ranging from moist woods and shaded river banks, to peat covered limestone in the uplands. In addition to Smith's first record listed above, there is another early site at Cloncarn near Magheraveely, where it was recorded by Meikle and co-workers in 1948.

Although it typically grows in permanently moist, sandy or clayey soils, surprisingly it has never been found on any of the many lakeshores in the VC, although further north in Scandinavia it does occur in such situations, plus in a wide range of other very different, often much drier habitats which it never occupies in Britain & Ireland (Jonsell et al. 2000, p. 24).

In Fermanagh, like several other horsetail species, eg E. palustre (Marsh Horsetail) and E. telmateia (Great Horsetail), E. hyemale appears to require some lateral water movement at its roots, either a slow seepage or a flushing of moderately base- or mineral-enriched spring water (Rose 1989; Brewis et al. 1996).

An unusual variant

In terms of habitat, E. hyemale is not a very variable species but one exceptional site occurs on the limestone plateau at Legacurragh above Florencecourt. Here a solitary plant of a completely prostrate form of E. hyemale grows on thin blanket bog peat developed directly over limestone pavement. According to Clive Jermy (pers. comm. 1995), this unusual prostrate form is known from Scottish dune systems and, as here, grows in flushed, shallow peat over limestone.

Reproduction

Fertile stems emerge along with sterile ones in May-June and are similar in appearance, except that they produce a small, black cone which bears a short sharp tip (ie an apiculus). Spores are not produced until early spring of the second year and, in common with all other Equisetum species in Britain & Ireland, reproduction and spread of E. hyemale is mainly (but not exclusively), vegetative, involving lateral growth of the rhizome and water dispersal of stem fragments (Praeger 1934).

Growth rate, silica content and rough stem texture

E. hyemale is said to grow and spread very slowly, even when well established (Page 1997, p. 451), yet at the site on Manyburns River in Fermanagh, and in similar places, the plant grows in abundance in thick clumps. In these situations it locally dominates the riverbank vegetation, presumably due to its tenacious rhizome and the longevity of the species.

The observed slow growth of this species is probably due to its very high silica requirement, which in turn is associated with the colourless siliceous tubercles and other physical structural features which give the plant its characteristic tough, evergreen stems their very rough, abrasive texture.

Uses and English common names

The English common names, 'Rough Horsetail' and 'Dutch Rush', both allude to the fact that from early days, at least from the 17th century onwards, the plant was greatly valued as a scourer, the equivalent of our present day wire-wool (Grieve 1931). E. hyemale stems were collected locally and sold in markets for scouring cooking pots and were also used by artists for fine polishing metal, wood and bone articles (Step & Jackson 1945) and thus the range of English common names 'Pewterwort', 'Shave-grass', 'Scouring-rush', 'Scrubby-grass' and 'Dishwashings' (Prior 1879; Britten & Holland 1886).

Rough Horsetail is mentioned by Gerard (1633) as being used by fletchers (arrow makers) and comb-makers to polish their finished articles. Other more frequent and abundant Equisetum species were also used for these purposes, eg E. arvense (Field Horsetail) and E. palustre and, undoubtedly, some of these common names (apart from 'Dutch Rush') would also have been locally applied to them as well. Grigson (1974) and Mabey (1996) both report that bundles of E. hyemale are still sold as scourers in continental European markets.

Being a slow growing, rather scarce species, commercial collecting in B & I must have very quickly reduced local populations of this horsetail, so that imports from or through the Netherlands became necessary to meet the commercial demand for scourers and hence the name 'Dutch Rush'.

Irish occurrence

Long after the commercial use of the species as a scourer ceased, E. hyemale remains a rare, local and apparently declining species in the whole of the British Isles. In Fermanagh, it occurs in just 12 scattered post-1975 tetrads. Elsewhere in N Ireland, E. hyemale is rather rare in Cos Antrim, Tyrone and Londonderry (H39, H36 and H40), and very rare in Cos Armagh and Down (H37 and H38) (NI Vascular Plant Database 2001). In the Republic of Ireland, Rough Horsetail (often referred to as 'Dutch Rush') is very rare and scattered, and is apparently declining here also.

British occurrence

In Britain, the species overall has a decidedly northern distribution and, while scarce and local even in the northern half of the island, it is very much more rare and obviously declining south of the Mersey-Humber line (Jermy et al. 1978; Page 1997).

European and world occurrence

The European distribution of E. hyemale is quite similar to that of E. sylvaticum (Wood Horsetail), being essentially northern and boreal and stretching from SE Greenland (where it was first found as recently as 1981), through to Iceland, the Faroes (but not the Arctic Isles), and throughout all of Scandinavia. It also extends south to Gibraltar (although only very thinly represented across the Iberian peninsula) and thence eastwards along the northern shores of the Mediterranean to Greece and N Turkey (Jalas & Suominen 1972, Map 30; Daniels & Van Herk 1984). The distribution then continues east through the Himalaya and much of N Asia to Japan and Central America (ie Mexico and Guatemala) (Hultén 1962, Map 174; Hultén & Fries 1986, Map 11; Jonsell et al. 2000).

Is it circumpolar?: Although E. hyemale is classified by Preston & Hill (1997) without qualification as Circumpolar Boreo-temperate, the species only qualifies as circumpolar if we consider the taxon in its very broadest sense. In Europe and in W & C Asia, the E. hyemale we know in Britain and Ireland is a moderately variable species, but in E Asia and especially in N America, it becomes a complex of several forms which, while their taxonomy is incompletely worked out and is a subject of disagreement, have been grouped by American taxonomists into two species, E. hyemale and E. laevigatum and their hybrid (E. × ferrissii). N American E. hyemale is then further subdivided into three varieties and three forma, none of which is identical with our Eurasian plant (Hultén 1962; Scoggan 1978, p. 130). Thus there exists an enormous void in the circumpolar occurrence of the Eurasian form of E. hyemale (ie our E. hyemale), throughout N America. In terms of the plant's plant geography, its presence further south in C America does absolutely nothing to fill this northern, Boreo-temperate gap.

Names

The genus name 'Equisetum' was coined by the ancient Roman writer, Pliny and is thought to have been first applied by him to E. arvense. It is a combination of two Latin words, 'equus', a horse and 'saetum', a bristle or hair, and it is thought to refer to the bristly appearance of the jointed stems with their whorled branches (Gilbert-Carter 1964; Grieve 1931). The same notion also gave origin to the English common name 'Horsetail', which is a direct translation of the medieval Latin name, 'cauda equina', under which it was sold in apothecary shops (Prior 1879; Grigson 1974).

The Latin specific epithet 'hyemale' or 'hiemale', means 'of winter', that is, 'reproducing in winter' (Gilbert-Carter 1964).

Threats

Clearance of wooded stream banks, or excessive trampling or grazing of the sites by cattle pose the two major threats. Drainage might also be significant in other areas of the British Isles.