Anyone who has visited the west of Cornwall at this time of year cannot have failed to be impressed by the beautiful drifts of yellow gorse flowers one sees everywhere. However, very few visitors have ever seen the remarkable phenomenon of blue gorse, or eythin glas as it is called in Cornish. The first reference to this is found in a poem in a 15th century manuscript housed in the British Library (AFD104), which contains a poem in which an honest Englishman is said to be mar danow avel eythen glas (“as rare as blue gorse”).
The first scientific observation of the phenomenon was by the botanist A.F.Day and reported in his now rather rare work Botanic Rareties of the West of England (Edinburgh: Morton, 1837). No explanation for the phenomenon has been generally accepted. An apparently perfectly normal gorse bush which is as yellow as its neighbours one day suddenly turns blue overnight. This only ever happens in early spring and the blueness fades after a few hours.
I was extremely fortunate to spot an example of eythin glas on a walk near Land’s End this afternoon.