Equisetum telmateia Ehrh., Great Horsetail

Account Summary

Growth form and preferred habitats

This imposing rhizomatous species always grows in colonies and the large size of the tall, sterile, annual, deciduous shoots, their abundant lateral branches and ivory-white stems make Great Horsetail both conspicuous and completely unmistakable. E. telmateia is closely tied to permanently wet soil, typically either poorly drained clay or shallow peat, which is more or less constantly flushed with base-rich, generally calcareous ground water springs or seepage emerging from overlying, more permeable sedimentary rocks (Brewis et al. 1996; Page 1997). It often grows along the edge of roadside hedges and ditches, on eroding river banks, or at the base of wooded cliffs where it is shaded or semi-shaded by overhanging tree and shrub branches. It is associated with man and some habitats he creates, and therefore is apophytic on clayey slopes of roadside banks, railway cuttings and embankments, provided there is the necessary degree of base-rich water seepage through the soil (Jonsell et al. 2000).

The ecological requirements and tolerances of Great Horsetail overlap quite closely with those of several other horsetails, since it commonly associates with E. palustre (Marsh Horsetail), less frequently with E. fluviatile (Water Horsetail) and rarely with E. hyemale (Rough Horsetail).

E. telmateia is essentially a lowland plant, unable to tolerate upland exposure and rarely found over 250 m, but the requirement for moving groundwater rich in calcium or other bases, together with the laws of gravity, confine it both geographically and geologically in any case.

Plant structure and spore production

The thick, fleshy-looking, white sterile stems of Great Horsetail can reach 2 m or more in height and are heavily furnished with whorls of long lateral branches. Despite their robust appearance, the tall, stout sterile stems are in fact very brittle, making the species intolerant of any trampling or grazing whatsoever (Sinker et al. 1985).

As in the case of E. arvense (Field Horsetail), separate, whitish-brown, unbranched fertile stems up to about 20 cm in height appear before the photosynthetic sterile stems in April and May. The cone-like fertile spikes are produced most abundantly on the drier, warmer, marginal areas of the typical habitat (Jonsell et al. 2000). The cone-bearing shoots are very ephemeral, typically sporing, withering and dying off within two weeks of their initial production (Jermy & Camus 1991; Page 1997).

The deeply running branched rhizomes of Great Horsetail are about 1.0 cm in diameter, have large air canals embedded in their conducting tissues, similar to those in E. palustre, and they bear numerous starch storage tubers at their nodes (Page 1997).

Vegetative and sexual reproduction

As with all other horsetails, the main form of reproduction is probably vegetative by means of the rhizome tubers and fragmentation of other parts of the plant. Since E. telmateia forms a number of rare or very rare hybrids with other Equisetum species, some successful spore germination and prothalial sexual reproduction must also occasionally take place (Page 1997).

Hybrids

E. telmateia is capable of forming hybrids, and does so very rarely with E. fluviatile (one record from Ireland), E. palustre (2 hexads in Co Sligo), E. sylvaticum (Wood Horsetail) (no Irish records) and E. arvense (again, no Irish records) (Stace et al. 2015).

Fermanagh occurrence

E. telmateia is the fourth most frequent and widespread horsetail in Fermanagh, occurring in 171 tetrads, 32.4% of those in the VC. Six tetrads contain pre-1976 records only. As the tetrad distribution map shows, it is widely distributed, especially in the S & W of the county. The most extensive stands in Fermanagh are along the shore road of Lower Lough Erne, below the Cliffs of Magho (also known as Poulaphouca). However, it occurs in quite a wide variety of habitats chiefly in limestone areas, including lakeshores, river and stream banks (especially in gullies), cliff bases, below waterfalls, in quarries and even along railway lines disused for over 50 years.

Toxins and uses

Like other horsetails, stands of E. telmateia contain large quantities of silicates and a variety of toxic principles, including alkaloids and an enzyme called 'thiaminase' that destroys thiamine (vitamin B) (Cooper & Johnson 1998). The plants are usually avoided or ignored by grazing horses, but owing to the smoothness and fleshy softness of its stems, it is said to be acceptable to cattle as food. The 18th century Swedish botanist Linnaeus commented that in N Sweden E. telmateia was cut and given to cows for fodder and that in Lapland reindeer would eat it, although horses always refused to do so (Grieve 1931).

There are reports of young stems of Great Horsetail being eaten like asparagus from Roman times onward, particularly by the starving poor. Unfortunately, as a vegetable they are neither palatable nor very nutritious and like other horsetails they undoubtedly contain toxins (Grieve 1931).

British and Irish occurrence

E. telmateia is frequent to locally abundant throughout most of the British Isles, although it is more occasional in the southern half of Ireland and is rare or absent in many parts of C, E and N Scotland (Jermy et al. 1978; Stace 1997; New Atlas).

European and world occurrence

Great Horsetail reaches the most northernly point of its European range at Caithness in Scotland (VC 109), and the European distribution extends southwards through W, C and S Europe to N Africa, Turkey, the Caucasus and eastwards to Iran. In the Pacific States of N America, it is represented by a separate subspecies, subsp. braunii (Milde) Hauke (Jalas & Suominen 1972, Map 39; Hultén 1958, Map 258; Hultén & Fries 1986, Map 20; Jonsell et al. 2000).

Names

The Latin specific epithet, 'telmateia' means 'of marshes', or 'of muddy waters' (Gledhill 1985). The few English common names that are specific to this species include 'Fox-tailed Asparagus' and 'Horse Pipes'. The former obviously refers to the similar appearance of the spikes of the young plants to a foxtail and the previously mentioned fact that both have been eaten by humans. This name first appeared in notes made by Lyte when he was preparing his Newe Herball (Lyte 1578), based on his translation of the French edition of Dodoens' Dutch language Cruydeboeck, that was originally published in Antwerp in 1554 (Britten & Holland 1886; Anderson 1977).

Threats

None.

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