Garlic mustard or Hedge garlic
Hedge garlic (Alliaria petiolate), Garlic mustard or Jack by the Hedge or Bóchoinneal in Irish is one of those plants that is regularly weeded without a moment’s thought for the spectacular contribution it makes to biodiversity in the garden and on the roadside. Alliaria means that it smells of garlic and indeed it does if the heart shaped, nettle-like leaves are crushed between forefinger and thumb. (1)
The flowers are crucifer which means that the four white petals are in the shape of a cross.
It is common in the East and the Centre of Ireland but not so common in the West.
The fruits are green pods and are visible now as flowers fade. (2)
During May the female orange tip butterflies search for Hedge garlic, Cuckooflower (Cardamine pratensis) and lay their eggs on the flower stalks of these plants. (3a;3b:3c)
About a week later the caterpillars emerge to eat the seed pods and seeds which the pollinated flowers produce. The caterpillars are very difficult to see because they are so well camouflaged, they look like the seed pods (4a;4b)
It only takes about four weeks for the caterpillars to grow fully. They will then leave the food-plant to find dry stems on which they will tie themselves by threads and change into chrysalises. They will stay like this for nine to ten months before emerging as butterflies to start cycle all over again.
Last Saturday we discovered ten orange-tip caterpillars on one hedge garlic plant. Most books I have read state that only one caterpillar is laid on a plant!