This is sometimes known as Fireweed, because it will often spring up in an area where there has been a bonfire. For this reason it is classified as a pioneer species, also as an opportunist species. In my bit of Ninewells wood, there are several areas where there has recently been a fire. After the Corsican Pines were felled there was a lot of brash lying about. This was largely caused by the removal of the little side branches on the pines prior to cutting them into suitable lengths for sale as timber, biofuel, or fencing material.
So the area was more or less covered with a thick layer of brash, and we got a man with a JCB to scrape it all up into big brash heaps and then to set them on fire. As it turned out only about half of the brash piles were ever burnt of because a change in wind direction meant that the burning had to stop because it would have risked setting fire to neighboring woods or worse two nearby houses.
Actually I am quite pleased because the brash heaps have provided a good little microhabitat, wrens use them for shelter and nesting and I am sure many invertebrates are also living in them. They are reducing in size quite quickly as they rot down and plants are starting to grow up out of them, so in a few years they will be all but gone.
Getting back to Rosebay willow herb, the brash heaps that were burnt off are now marked by tall pink spikes of Willow herb, mostly of the Rosebay type but there are also some others with much smaller more insignificant flowers. In a few years time they will probably decline as the influence of the bonfire ( higher levels of potash) declines and the young trees grow up and shade increases.
This plant is a perennial, and has creeping rhizomes in the soil. It has long thin leaves which is where it gets its scientific name ‘angustifolium’ from. It grows quite tall, up to about 1.5 M high and has beautiful spikes of purple flowers. These normally come out in early summer but last quite a long time, they are much frequented by the bees and other insects. After the flowers are over long thin seed pods develop, and these eventually split to release vast quantities of tiny seeds, about 300 to 400 per capsule and 80,000 per plant. The seeds have silky hairs to aid wind dispersal and are very easily spread by the wind.
After the second world war when there were lots of bomb sites around this plant spread rapidly to colonise these often inner city places. Its spread was aided by railway lines which in those days were still populated by steam trains and thus were subject to frequent fire from the sparks generated from the coal furnaces on the trains. These were then colonised and the seeds were quickly blown along by the trains. During that period it became known as Bombweed, that has fortunately declined in recent years.
Even in the early 1960s when I lived in the east end of London there were still quite a lot of bomb sites around and as an ardent collector of butterflies and moths, ( sorry but all small boys of that era collected something…. no internet…. and if you were into wildlife you collected eggs, or moths, or butterflies, or shells but collecting is what you did.) I used to frequent these areas in search of specimens. The flowers attracted some butterflies, but what I was really looking out for were the caterpillars of various moths which feed on the leaves. Four different Hawk moths use the leaves as a food plant, the Elephant Hawk moth, the Small Elephant Hawk moth, the Striped Hawk moth the Bedstraw Hawk moth, along with several other moths. Incidentally another common coloniser of bomb sites was the Buddleia bush which also attracts lots of butterflies, so it was a happy hunting ground for a country boy who had been uprooted from a small Essex village and then found himself living just round the corner from West Ham football ground and almost within the sound of Bow bells.
From memory I only recall finding the Elephant Hawk moth,(the one in the photo above). The others are quite rare. I did also get lots of butterflies from the Buddleia flowers, this is possibly why the butterflies are somewhat rarer nowadays, though I tend to think pesticides and modern farming methods have more to do with it than small boys armed with a net made from your mother’s old stockings and a jar full of Laurel leaves.
Well this post has covered all sorts of things some of which have been about Rosebay Willow herb and lots of it has been me rambling on about stuff which is at best loosely related to the plant….. If you have got this far then it was presumably worth it.
To check out other wildflowers found in the woods of the Wye valley and Ninewells wood click Woodland Wildflowers of the Wye valley and Monmouthshire.