Armoracia rusticana P. Gaertn., B. Mey. & Scherb., Horse-radish
Account Summary
Introduced, archaeophyte, naturalised from cultivation, very rare.
July 1982; Northridge, R.H.; roadside at Granshagh, 6 km SSW of Enniskillen.
June to August.
Growth form, reproduction and preferred habitats
The large, erect, wavy, coarsely or bluntly toothed, shiny, long-stalked basal leaves of this perennial give off a strongly pungent, quite unmistakable smell if bruised. Although occasionally it produces a tall, leafy spike of numerous self-incompatible, sweetly scented, white flowers from May onwards, it is almost always completely sterile and, if formed, the small globular seed pods never (or hardly ever) ripen in Britain and Ireland (Weber 1949; Rich 1991). Despite this, Horse-radish, which develops the long, tapering, fleshy but hard, white, pungent-flavoured tap root for which it is culinary famed, plus numerous deeply penetrating, thin, secondary roots branching from it, manages to reproduce quite efficiently and vegetatively by means of these underground organs.
Very small fragments of secondary root material are sufficient for propagation. Uozumi et al. (1992) found that root fragments of A. rusticana with an apical meristem or a branch, could efficiently regenerate to form whole plants, and that fragments more than 5 mm in length possessed a high shoot-forming ability. Root fragments are readily dispersed in transported soil, mud on tools and otherwise by man the cultivator. Once transferred in this manner, often to other cultivated ground, waste ground near habitation or, as in Fermanagh, to roadsides where soil has been dumped, stored or spread, individual established plants can prove extremely persistent, even for example, in overgrown, abandoned kitchen-gardens of long-derelict houses.
Many gardeners regard the plant as eternal, rather than perennial, for once introduced to a vegetable patch it can become a pernicious weed, virtually impossible to get rid of without resort to repeated applications of powerful systemic herbicide. To give an indication of potential root penetration, Edlin (1951, p. 108) tells of excavating roots in a cutting in the English chalk, to a depth of 6 feet [2 m]. The secret of cultivating it is to lift the plant every year and to store it over winter in sand. Alternatively, it should be grown in a closed container.
Fermanagh occurrences
There are just four records of Horse-radish, all in non-garden, roadside settings in the Fermanagh Flora Database and all recorded by RHN. Apart from the first, which was in a more rural setting, the remainder are all near habitation around Enniskillen and in two villages in the SE of the VC. The details of these records are: Lisnaskea, July 1988; by Silverhill Bridge, on the NW outskirts of Enniskillen, August 1988; and, just S of Teemore village, June 2002.
Although A. rusticana is extremely persistent when established, it is not an invasive species when left unmanaged, at least in Ireland. Even well established plants tend either to be solitary or to display little vegetative spread (Reynolds 2002).
Variation
Being almost entirely sterile and clonal, it is not surprising that several distinct leaf forms of A. rusticana occur and are perpetuated by its asexual reproduction. The leaf forms include, for example, a distinction between those that are crinkled in texture and markedly notched at the base (ie cordate) and others which have smooth surfaces and taper gradually into the petiole (ie cuneate). Illustrations of both these Horse-radish leaf forms are found in 16th century herbals, proving that the clonal distinctions are old and maybe of ancient origin (Courter & Rhodes 1969).
The problem of disease transmission
Another more unwelcome consequence of continual asexual propagation in a crop plant is that microbial diseases are readily transmitted in the propagated maternal tissue. Horse-radish is widely cultivated in the USA and produces a root crop of good quality in spite of being very susceptible to White Blister Rust and Horseradish (= Turnip) Mosaic Virus (Weber 1949). Pound (1948) showed that 100% of the then most frequently cultivated clone in the USA was virus infected and a great desire arose to produce virus-free Horseradish seed and then to breed greater disease resistance into the crop.
Seed sterility, genetic cytotype and possible hybrid origin
The high level (but not absolute) seed sterility of A. rusticana has been shown to arise from meiotic irregularities in the formation of male and female sex cells, including only partial pairing of chromosomes and aneuploidy: the plant has a normal chromosome count of 2n=4x=32, but occasional plants have only 2n=28 (Easterly 1963). Only twelve viable seeds were harvested following approximately 10,000 crosses carried out by Weber (1949). Carrying this work on, Stokes (1955) found that failure to develop viable seed following fertilization was due mainly to endosperm-maternal tissue incompatibility, resulting in endosperm failure and, less frequently, in embryo abortion. These facts point to the possibility that A. rusticana may be of hybrid origin, or indeed it might itself be a hybrid rather than a true species (Courter & Rhodes 1969).
While over the years Horseradish has been transferred by taxonomists through numerous related genera, e.g Thlaspi, Raphanus, Cochlearia, Radicula, Nasturtium and Rorripa, if it were of hybrid origin, or an actual hybrid itself, no one has yet suggested the possible parents. Molecular isozyme genetic analysis using nuclear and chloroplast DNA by Franzke et al. (1998) has shown A. rusticana is closely related to the genus Rorippa.
There is a considerable body of active genetic research involving A. rusticana, much of it biochemical and very technical, or associated with tissue culture.
Irish occurrence
Although A. rusticana has been found at least once in 35 of the 40 Irish VCs (Scannell & Synnott 1987; Reynolds 2002), it is really quite rarely recorded on this island, being found mainly on roadsides, waste ground or dumping sites near the larger cities and towns, or in coastal locations where it may originate in fly-dumped household and garden refuse (a nasty, dirty habit, and unfortunately all too prevalent), or like many other members of the Brassicaceae it may just prefer the relatively open, sandy soil of such situations. Support for this latter suggestion comes from the fact that in other parts of these islands it sometimes colonises sandy seashores, railways and river-banks (D.A. Pearman, in: Preston et al. 2002). De Candolle (1884) noted the same tolerance of salty soils in E Russia. Indeed, the very word 'armoracia', which has been applied to the plant both as a generic name and specific epithet, is formed from the Celtic words 'ar' meaning 'near', mor, 'the sea', and rich, 'against', ie a plant growing near the sea (Barton & Castle 1877).
In Northern Ireland, the relative scarcity of the species is indicated by the fact that it was first recorded in Fermanagh as late as 1982, in Down (H38) in 1913, but with no second station until 1946, and in Antrim (H39) in 1965 (Kertland & Lambert 1972; Hackney et al. 1992). The Northern Ireland Flora Website shows A. rusticana is now quite well represented along the coastal shores of Down and Antrim, but is much more rare and scattered inland.
British occurrence
While it is generally regarded as a hardy perennial, A. rusticana is essentially confined to the lowland situations in which it is or has been cultivated and, in Britain, it is so much more widespread in England compared with Wales and Scotland (Preston et al. 2002), to the extent that one might even dare postulate a cultural divide in Horseradish sauce use by the populace!
Toxicity
The pungent aroma and flavour of the root and leaves of this table condiment are due to two glucosides, sinigrin (allyl glucosinolate) and 2-phenylethyl glucosinolate. These poisonous principles are similar to mustard oil and, when hydrolysed, are potent irritants of the eyes and skin and can cause lethal poisoning of stock animals, including cattle, ponies and pigs (Cooper & Johnson 1998).
Uses
A. rusticana, under a variety of early names, but clearly referring to this plant, was familiar enough as a medicine to the 16th century English botanical Herbal authors Turner (1551) and Gerard (1597), and already both knew of it as an escape from cultivation (Grigson 1987). Thus the plant is nowadays regarded an archaeophyte in Britain and Ireland (ie an ancient pre-1500 AD introduction). Originally, it was a purely medicinal herb with a reputation as a very strong diuretic for treating dropsy, sciatica, gout and stones, a usage stretching back to Dioscorides in the first century AD (Grieve 1931; Courter & Rhodes 1969).
The first mention of the plant's cultivation in a mediaeval European herbal is by Albertus (a physician so highly regarded he was also known in his own lifetime as 'Albertus Magnus'), his work dating from 1260 (Harvey 1981). However, Gerard (1597) reported that in Germany the grated root, mixed with vinegar, was then being put to its present culinary sauce use for meat and fish, a practice he appears to report to his countrymen as something novel. By 1640, when Parkinson wrote his early gardening book cum herbal, Theatrum botanicum, he was aware of the plant's condiment use in England and he issued a warning on the strength of its flavour.
Making horseradish sauce from the raw vegetable can be a traumatic experience, as the fumes from the grated root are much worse than very powerful onions. A modern electric food-processor is the answer, and Mabey (1972, p. 62) provides a good recipe.
European occurrence
Like almost all such early cultivated introductions, the original 'wild' distribution of A. rusticana has been obscured by its long association with man. In a masterly combination of geography and philological analysis, De Candolle (1884, pp. 34-6) pointed to the fact that the plant (he called it Cochlearia Armoracia) was widely spread over an area of N, W and C Europe (nowadays mapped for Flora Europaea from Finland (c. 67°N) to C Spain and S Italy, but rare and very scattered in the Mediterranean basin (Jalas & Suominen 1994)) and beyond this to the Caspian Sea, the deserts of Cuman and in, "several localities in Turkey in Europe, near Enos, for instance, where it abounds on the sea-shore". Nevertheless, as one moved westwards, De Candolle noted the plant became increasingly rare and more scattered; hence he concluded that A. rusticana was not indigenous in W Europe.
Possible area of origin
De Candolle (1884) also identified the word 'chren', common in the numerous Slavic languages of E Europe, as the most primitive name for Horse-radish, a name that was introduced into German dialects as 'kren', 'kreen' and in French as 'cran' and 'cranson'. Another name used in Germany is 'Meerretig', in Holland 'meer-radys', which becomes 'meridi' in the Italian Swiss dialect, all literally meaning 'sea-radish', but these De Candolle regarded as not primitive like 'chren'.
On this basis he concluded that the most probable place of origin was the temperate region of E Europe, from thence its cultivation had been spread westwards for about a thousand years.
Due in part to their original vagueness, and to the numerous subsequent changes and introduced errors in names and uses perpetrated by copyists and later scholars upon the texts of ancient herbal authors over the intervening centuries, it is often impossible to identify with certainty which of several related species the oldest works are referring to, the belief is that this plant was mentioned by Dioscorides (1st century AD), yet not by Theophrastus (372-287 BC) and thus it has only been cultivated for less than two thousand years (De Candolle 1884; Courter & Rhodes 1969).
Names
As noted above, there is a suggestion that the name 'Armoracia' is derived from Celtic words meaning 'by the sea' (Barton & Castle 1877), but we regard this as doubtful (Deirdre Forbes, pers. comm.). Other authorities suggest the name is Greek or Latin in origin, and that it was first applied by Pliny, not to this species which he called Persicon napy (Courter & Rhodes 1969), but to another unidentified radish-like plant, possibly Raphanus raphanistrum (Gilbert-Carter 1964; Stearn 1992). The specific epithet 'rusticana' is derived from Latin, and like the word 'rustic', means 'of the countryside', or 'of wild places' (Gledhill 1985).
The English common name 'Horseradish' was first given by Gerard (1597). The word 'horse' commonly applied to a name in this manner, means it is a larger, coarser or stronger variety of plant. Thus 'Horseradish' means 'a strong radish', which is of course apt in this case. Grigson (1974 & 1987) has also suggested that Gerard may have coined the name from a mistranslation of the German 'Meerettish', which means 'Sea-radish', in the sense of a radish or root from foreign parts, ie 'Overseas Radish'. Grigson seems to have thought that Gerard took the 'meer' element to mean 'mare', a female horse, or alternatively as 'mähre', which translates as 'an old horse', as if it referred to the rankness and toughness of the roots (Courter & Rhodes 1969).
The name 'Radish' is derived from Latin 'radix' or the Italian 'radice', meaning a plant valued for its root (Prior 1879). It was spelt 'radyce', which is the Old English form, in Turner's (1538) 'Libellus de re herbaria novus' (Rydén et al. 1999, p. 80-81 & Table 1, p. 121).
Previous English Common names included 'Redcole' or 'Redco' (Turner 1551), or 'Redcoll', 'Redcoal' 'Radcole' and 'Rotcoll', 'Cole' commonly referring to cabbage and other members of the Brassicaceae (Britten & Holland 1886). Lyte (1578) called it 'Rayfort' and 'Mountain Radish', from the French 'raifort', meaning 'strong root' (Grigson 1987; Courter & Rhodes 1969).
Threats
None.