Rosebay willowherb has begun its magenta march over the countryside which must mean that the school holidays are about to start. No plant is so synonymous with high summer, but it hasn’t always been so. Named after its long narrow willow like leaves, Chamerion angustifolium, was once a rare native species until it suddenly began to expand around 1860 for reasons which are still not entirely understood.
A century ago, during World War 1, the plant exploded in areas where trees were felled for the war effort and later, in World War 11, Rosebay willowherb renewed its invasion by colonising the areas after bombing raids where it came to be known as fireweed. However, its expansion really began when it was spread along the railway line rather like buddleia. Unlike other members of the willowherb family e.g. Great Willowherb (Epilobium hirsutum) and the smaller Broad Leaved Willowherb (Epilobium montanum) which readily cross breed, Rosebay Willowherb hybridises with nothing. There is also a rather lovely white form, Chamerion angustifolium ‘Album’, which is described as slowly invasive but not troublesome, and both types are important food plants for the beautiful elephant hawk moth.
In September, as a new term starts, the long pink seed pods will open from the top like a banana to release 20,000 parachuted seeds from every plant. Flying off to pastures new, the fluffy storms are known as ‘sugar fairies’ in the north which is perhaps a link to the sugary edible pith which can be extracted from the ripe stems.