Conopodium majus (Gouan) Loret.

Common Name: Pignut

Family: Apiaceae

Plant description

Conopodium majus is a small herbaceous perennial common in woods, grasslands, and hedgerows across Europe. It flowers from May to June producing white flowers in compound umbels and has finely divided leaves. The stem terminates in a single tuber up to 20cm below ground with thin fibrous roots growing across its surface (Hather 1993). This storage organ is edible with a nutty flavour similar to chestnut and available all year round.

Tuber description

The tubers are irregularly spherical and can grow up to 3cm in diameter. There is one large root attachment scar 2-4mm across on each tuber, sometimes the root base is retained. On some tubers there is small hollow around the main root attachment. Fibrous roots, c.1mm across, tend to be concentrated on nodular projections. There can be multiple fibrous roots from the same node, leaving either attachment scars or root stubs. The surface, if preserved, is smooth, with no scale leaf scars or annual rings.

Charring causes considerable distortion of the internal anatomy, particularly in tubers charred from a fresh state. Large vesicles radiate from the centre of the tuber and also form tangentially beneath the epidermal layers. C. majus tubers are produced by secondary growth. Groups of vessels are arranged in the central core opposite rounded phloem regions and can become solid carbon when charred, with vesicles between vessels. (Hather 1991, p. 60)

Archaeobotanical information

Conopodium majus has been found archaeologically. It has been identified at Mesolithic Halsskov, Denmark (Kubiak Martens 2002), Neolithic Windmill Hill UK (Fairbairn 1999) and Bronze Age Barrow Hills and Mile Oak UK (Moffett 1991, Hinton 2002). At each context pignut tubers were interpreted as a potential food resource, with possible ritual connotations in the Barrow Hills burial. When collecting C. majus tubers, the plant cannot be simply pulled out of the ground by its stem, it needs to be dug out from the soil which suggests that their presence in archaeological contexts was not accidental. Underground, the stem forms a right angle to the tuber and so detaches easily from tuber when pulled which makes careful digging to locate the tuber necessary (Mears and Hillman 2007).

The tubers can be harvested throughout the year however they would be most easily collected in spring and summer when the plants’ above ground tissue is visible (Fairbairn 1999). Pignut tubers can be eaten raw or cooked and have a nutty flavour. The tubers grow at a depth that makes it unlikely they would be regularly collected as tinder with other grassland plants unless turves were being burnt (Moffett 1991). Bunium bulbocastanum L., the great pignut is a related tuberous species of the Apiaceae and is morphologically similar to C. majus however B. bulbocastanum has a more restricted habitat distribution, present in chalk grasslands (Moffett 1999).

Conopodium majus. Collected Spring 2008 by J. Hodgson in Hathersage, UK. Scale 2cm. Photo C. Longford.
Conopodium majus modern material dried then charred at 230oC for 3 hours. Scale 2mm. Magnification X Collected by J. Hodgson Spring 2008, Hathersage, UK. Photo C. Longford.