Corncockle: a noxious weed in medieval Ireland?

Corncockle (from Wikimedia Commons)

Corncockle (Agrostemma githago) has been in the news recently after the BBC programme, Countryfile, offered viewers free packets of wild flower seeds via the Grow Wild project run by Royal Botanic Gardens Kew. These packets included seeds of corncockle, a colourful wild flower. Corncockle can, however, be poisonous, hence the kerfuffle. Interestingly, quite a number of our most popular garden plants are poisonous, including daffodils, ivy, lupins and foxgloves. In the case of corncockle, you would need to ingest large quantities of the seed to be in danger, so it remains a favourite of gardeners wishing to add colour to a garden border.

But there was a time when corncockle was a troublesome plant because of its poisonous qualities. During the medieval period in Ireland (c. AD 1150 to 1500) in particular, corncockle was an abundant arable weed, growing alongside crops and sometimes inadvertently harvested. Corncockle seeds are quite similar in size to cereal grains, so great effort would have been required to remove corncockle seeds from cereal grains when preparing foods. If corncockle seeds were not removed, the seeds would have affected both the colour and the taste of flour, and if eaten in large enough quantities, could have affected the health of the consumer. Indeed Gerard’s 16th century Herball (history of plants) noted “what hurt it doth among corne, the spoile of bread, as well in colour, taste, and unwholesomnesse, is better knowne than desired” (Woodward 1994, 252). 

Corncockle seeds (from Wikimedia Commons)

Despite the importance of removing corncockle seeds from cereals, our ancestors were not always successful in this regard. Corncockle seeds have been found during scientific analysis of deposits from archaeological excavations in Ireland, most recently at the just published Hiberno-Norse (Viking) and medieval excavations at South Main Street in Cork. My analysis of deposits discovered that tiny fragments of corncockle seeds were present in what appears to be cess (human faeces) at South Main Street (McClatchie 2014). It is likely that corncockle was consumed because the fragmented seeds had not been properly removed from the cereal grains. Similarly, pellets of hardened faeces from Hiberno-Norse Dublin contained fragments of corncockle seeds, suggesting that they were also consumed inadvertently with cereals (Geraghty 1996, 31).


So there was a time when care was needed in dealing with corncockle. But due to the increased use of herbicides and other grain cleaning techniques, corncockle is now largely extinct as an arable weed in Ireland, and hence there is little chance of it being incorporated into foods. The rarity of corncockle, as well as its beauty, now encourages gardeners to continue propagation of this interesting plant.

References
Geraghty, S (1996) Viking Dublin: botanical evidence from Fishamble Street. Royal Irish Academy: Dublin 

McClatchie, M (2014) 9.1.1 Non-wood plant macro-remains, 429-447. In MF Hurley and C Brett (eds), Archaeological excavations at South Main Street 2003-2005. Cork City Council: Cork

Woodward, M (ed.) (1994) Gerard's Herbal. Senate: London