Pignut and Chimney Sweepers

Chimney Sweeper (Odezia atrata)

Chimney Sweeper (Odezia atrata)

Pignut (Conopodium majus)

Pignut (Conopodium majus)

I would like to introduce you to just one tiny part of the food chain. It is a relationship between a rather interesting plant and a curious looking moth, that exist together in certain habitats, and which make a wonderful sight at this time of year. The Pignut (Conopodium majus) and the Chimney Sweeper (Odezia atrata).

Pignut is a small wildflower that can be found in open woodland, ungrazed dry grassland and amongst hedgerows. It is a low growing plant and when it’s not in flower, the small carrot-like leaves could easily be overlooked. In fact, after flowering, most of the visible part of the plant disappears, leaving only the roots and tuber underground. This is where the plant gets its name; from the buried ‘nut’ at the base of the plant, which pigs dig through the ground to find and eat.

And it’s not just pigs that will eat the Pignut tuber! It can be eaten raw and is apparently quite flavoursome, tasting like a combination of celery and hazelnut, with a hotness similar to that which you get from radishes. However, care should be taken because without careful examination this plant could be confused with poisonous Hemlock Water Dropwort (Oenanthe crocata), which is another member of the carrot family.

From April through to June, Pignut produces a spray of delicate white flowers, clustered together at the end of long stalks that join lower down on the main stem. These are the ‘umbels’ that characterise this group. The flowers are attractive to a range of insects including solider beetles, hoverflies, and moths.

And it is here that we are introduced to the Chimney Sweeper Moth. Like Pignut, it is small and could easily be overlooked. The larvae are tiny and green, and are found from April to June eating the flowers or seeds of Pignut. A single generation of Chimney sweepers then fly during the daytime in June and July, on fast fluttering wings. They are sun-loving moths and are especially active on days with bright sunshine.

The Chimney sweepers are sooty black all over (hence their name), except for the white fringing at the tips of the forewings. I think this makes the chimney sweeper look like a white moth that has thrown on a black cloak. The drab colour and lack of pattern could render these moths unremarkable, but to me the swift flight of these delicate black moths through fields of white flowers is a delight to watch.

Chimney sweeper moths are locally distributed throughout most of Britain, but need their food-plant, so are restricted to where pignut can be found growing. At Brynna Woods and Llanharan Marsh Nature Reserve I first discovered Pignut in the south meadow, dotted amongst the Bluebells, Buttercups and Sorrel. My first Chimney sweeper sighting soon followed, and when I discovered that the moth was there because of the Pignut, I enjoyed these findings even more.

I think this is because I had appreciated the moth, and the plant, each in its own right, but to discover that they were connected made them even more valuable. Things in isolation can be amazing, but learning about the bigger picture gives us the perspective we need to fully appreciate what we have. The south meadow at Brynna is a little community in its own right and the dependence of the Chimney sweeper on the Pignut is just one small example of the kind of relationships that exist in nature.