Agrostemma githago L., Corncockle
Account Summary
Introduction, archaeophyte grain contaminant, now a very rare casual. Native range uncertain due to spread with early arable agriculture, possibly E Mediterranean, but very widely naturalised and now circumpolar boreo-temperate and widespread in the southern hemisphere.
1902; Abraham, J.T. & McCullagh, F.J.; Gubbaroe Point, Lower Lough Erne.
Growth form and preferred habitats
This rather handsome, purple/pink-flowered, ancient introduced annual grows erect, 30-100 cm, sparingly branched from a stout taproot. The narrow leaves and flowering stems are covered with white appressed hairs. The British and Irish distribution suggests it prefers lime-rich loam or light sandy sites, but it can grow in any soil. In earlier days, it was an important, widespread weed of cereals and other arable crops, especially wheat and rye. As a consequence of this, it often grew on field margins and appeared as a ruderal on disturbed, open, wayside habitats. Nowadays, it sometimes appears on steep, sandy slopes where erosion continually keeps the habitat open (Sinker et al. 1985).
Weed populations of this markedly anthropochorous species declined very rapidly after the introduction of improved seed cleaning methods and increased use of herbicides in the 1930-60 period. Corncockle is a weak competitor, not growing well in dense fields of fertilized crops (Jonsell et al. 2001). In the last 100 years in Britain & Ireland, it has been reduced to a rare, casual ruderal, confined to open wayside situations or gardens, where it is increasingly found as a component of sown wild-flower seed mixtures.
Flowering reproduction
The plant flowers from June to August and has pointed sepals that project appreciably beyond the five petals of the 2-5 cm diameter corolla. The flower is protandrous, and while visited by butterflies, it is largely automatically self-pollinated (Clapham et al. 1987; Jonsell et al. 2001). The capsule is ovoid and protrudes slightly from the calyx tube. It opens by splitting into five valves. The seeds are large, oval and flattened, about 3 mm in length. They are brownish-black or black in colour and are covered with wart-like protuberances. Each fruit capsule contains around 25 seeds.
Seed survival
The survey of soil seed banks in NW Europe provided seven estimates for A. githago, six of which considered dormant seed transient and one reckoned it short-term persistent, ie it may survive more than one year but less than five (Thompson et al. 1997). Thus there is no persistent soil seed bank, germination generally occurring within a few weeks of release from the plant. There are reports, however, that A. githago reappears from time to time when soil is disturbed, and in former arable fields (Sinker et al. 1985). This suggests a small proportion of seed may be long-term persistent in the soil seed bank.
Variation and taxonomy
There is not much variation over its large geographic range. The species has been moved to and from two alternative genera, Lychnis in the past, and Silene more recently. Jonsell et al. (2001), Stace (2010) and Sell & Murrell (2018) all keep it in Agrostemma L.
Fossil record
Records in Britain & Ireland are almost all of seed and date from the Roman period onwards. One pollen record, from Old Buckenham, is from levels considered to be Iron Age, Anglo-Saxon and Norman ages, along with abundant evidence of arable cultivation. There is no evidence of natural status: the abundant fossil seeds are always associated with a local collection of weeds of cultivation (Godwin 1975).
Toxicity
In the past, Corncockle was an important cause of animal and human poisoning. Previous to its decline, when A. githago was a plentiful weed of cereal crops, its seeds used to be threshed out with cereal grains and either sown with them for the next crop, or ground with them for flour. Unfortunately, the Corncockle seed contains high levels of toxic colloidal glycosides with the properties of saponins. These saponins are not inactivated by heat, and bread made from flour contaminated by A. githago seed can cause poisoning. The flour is discoloured a greyish hue, has a bitter taste and an unpleasant odour (Cooper & Johnson 1998). Although nowadays A. githago is of much rarer occurrence, in Poland there were 30 outbreaks of poisoning by it between 1951 and 1963, with high mortality among pigs, cattle, horses, fowl, geese and ducks (Cooper & Johnson 1998, p. 54).
In humans, a chronic type of poisoning called 'githagism' can occur after consuming saponin-contaminated flour. This involves weight loss, lassitude and gastrointestinal disturbances, including ulceration and frothy diarrhoea. Death can occur if the contaminated diet is continued (Cooper & Johnson 1998). It has been suggested that the high saponin content of contaminated flour may also have caused susceptibility to leprosy (Godwin 1975, p. 146).
Uses
Despite the severe toxicity of its irritant saponin poison, according to Grieve (1931) in the past A. githago was used in herbal medicine as a supposed cure for dropsy and jaundice. Its use by allopathic herbalists has been discontinued for obvious reasons, but in homoeopathy a trituration of the seeds has been used in treating paralysis and gastritis (Grieve 1931, p. 223). On the other hand, Allen & Hatfield (2004) dismissed as a probable error the very suggestion that A. githago ever had a role in herbal or folk medicine anywhere in the British Isles.
Fermanagh occurrence
There are just two records of A. githago in the Fermanagh Flora Database. The original early find by Abraham and his co-worker McCullagh on the shore of Lower Lough Erne as given above, and secondly in a recent patch of roadside sown with a 'wild flower seed mix' at Drumawill in Enniskillen, on the Sligo Road, which was found by RHN and HJN on 14 September 2003. Corncockle forms a regular component of such seed mixes and has recently appeared in roadside plantings in other Irish counties, eg within Birr town, Co Offaly in 2017.
Irish occurrence
In the 16th century, A. githago was regarded as a menace to husbandry and one of the worst weeds (Salisbury 1964). It was still a frequent and widespread cornfield weed in Ireland in the late 19th century, especially in light, sandy soils (Praeger 1901). It was suggested it was "usually introduced with vetches, in which crop it appears to be more abundant than in corn" (Colgan & Scully 1898). The noticeable decline in the population was noted in The Botanist in Ireland where the author commented on the distribution in the country being "rarer in the centre" (Praeger 1934).
A. githago is now considered more or less extinct in the wild in Ireland, but prior to 1950 it still was a relatively common, or at least a familiar weed of grain fields in all but eight VCs across the island (Cen Cat Fl Ir 2). The distinctly patchy display of old records plotted for Ireland in the New Atlas suggests it probably was never all that frequent or abundant, apart that is, from in the major cereal growing areas of the country, in SE of the island and in the Lecale peninsula of Co Down.
Apart from the two Fermanagh records already mentioned, the New Atlas map records just seven post-1987 hectads elsewhere in Ireland. The closest stations to Fermanagh were a few plants on disturbed ground at Belladrihid Bridge, Co Sligo (H28), found in 1999, and in a disused limestone quarry at Annahaia, in Co Monaghan (H32), dated post-1994, regarded by the finder, Ian McNeill, as probably discarded garden material (Cat Alien Pl Ir).
British occurrence
The New Atlas map shows A. githago surviving scattered throughout most of lowland Britain, but with a greater frequency in areas of limestone geology and the region of the map south of a line between Liverpool and Hull. It has been suggested that A. githago has some unknown biological or ecological link with the Rye crop, and that the rapid decline of the weed in the late 19th century, which preceded the intensification of agriculture, might be due to the move away from planting Rye that definitely occurred (Godwin 1975). Nowadays, A. githago is either a rare casual of waysides, or it is found in deliberately sown wild flower seed mixtures in gardens and municipal plantings. In England, it is also maintained in special agricultural Nature Reserves (Firbank 1988).
European and world occurrence
The centre of origin of A. githago is unknown, but it is presumed likely that it arose somewhere in the E Mediterranean region, possibly derived from its near relative A. gracile Boiss. In W Europe, Corncockle was one of a number of contaminants of crop seed spread by agriculture in ancient times which has in the last 60-100 years declined to rarity or extinction. The European distribution map published by Jalas & Suominen (1986, Map 1022) is particularly useful, since it indicates where the species is now regarded as extinct, or probably extinct, or not recorded since 1930. This shows A. githago extinct or almost so in Scandinavia, most of Britain & Ireland, N Germany, Holland, Belgium and in N, W & S France, although surviving and widespread in Spain, Portugal, Italy and European areas further east.
Hultén & Fries (1986, Map 779) describe A. githago as indigenous in Eurasia but also note this rapid decline in distribution. Their map shows A. githago as very widespread throughout C, W & E Europe but thinning northwards into Scandinavia. The map also shows the species widespread in C Asia, where presumably the limit of its native range lies. Elsewhere the species has been spread by arable agriculture to N & S America, the Far East of Asia, including Japan and Korea, C & S Africa, New Zealand and the Falkland Isles.
Names
The genus name 'Agrostemma' is a combination of two Greek words 'agros', meaning 'field', and 'stĕmma', 'crown', 'garland' or 'wreath', a reference to the beauty of the flowers − considered suited for garlands of wild flowers (Johnson & Smith 1946; Gilbert-Carter 1964; Stearn 1982). The Latin specific epithet 'githago' is an old genus name of the plant and is probably a combination of two words, 'git' or 'gith', a name given by Pliny to Nigella sativa (Black Cumin), and '-āgō', a common suffix in plant names. The word combination 'githago' is intended to indicate the similarity of the black seeds of the two plants, both of which were used in herbal medicine (Gilbert-Carter 1964).
A wide range of English common names exist for A. githago, Grigson (1955, 1987) listing 20 from around Britain & Ireland. The name 'Corn Cockle' or 'Cockle-weed' is thought to date from the 18th century, the earlier form being simply 'Cockle', from the Anglo-Saxon or Old English 'Coccel', perhaps connected with cock, the bird, but later applied to weeds generally, and especially to 'Corn Pink', another common name for A. githago (Prior 1879). There are 21 English common names given by Britten & Holland (1886) for Lychnis githago (one of several synonyms for Agrostemma githago). These include 'Gith', 'Gye' and 'Field Nigella', which recall the Pliny connection with the black seed mentioned above.
Threats
No threat to A. githago itself, but if the planting of so-called 'wild-flower seed-mixes' containing it continues and becomes more fashionable, this poisonous species could escape cultivation, increase and become a nuisance.