Rosebay Willowherb

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Wild Flower of the Week

Rosebay willowherb

The tall, mauve flower spikes of rosebay willow herb can often be seen in thick stands in woodland clearings, roadside verges, grassland and waste ground. A very successful coloniser, it has increased  from being a scarce woodland plant to its present abundance. This started with the railways as it readily colonises burnt stretches of banking which often resulted from sparks from steam locomotives. A single plant produces up to 20,000 wind borne seeds which can land and germinate miles from the parent. It readily travels up railway lines, the seeds blown along by the turbulence from trains. Rosebay  took  hold in London just after World War 2 when it invaded waste ground, often ground that was bombed in German air-raids. Its ability to colonise land that has burnt led to the name “Fireweed”. It became the county flower of London. As it has a different flower structure to the other willow herbs, it is botanically Chamerion not Epilobium angustifolium.