Weld: a common ‘weed’, with a fascinating dyeing history
I have a fondness for walking the Washburn valley. This 26km (16 mile) tributary of the Wharfe lies just to the north of Otley. If you avoid the busy paths around Swinsty and Fewston reservoirs, it is both peaceful and beautiful, with a bonus of being close to home, which explains why we are frequent visitors. While out walking last week, we stop for a picnic lunch on the grassy dam bank of Swinsty reservoir, and I am struck by the rich variety of flowers. Recent engineering works has left the soil disturbed, and given a chance for early colonisers to germinate, grow and flower. The most noticeable early coloniser, although I suspect ignored by most, is Weld (Reseda luteola). This stiffly erect, yellow-green plant grows up to 1.5 metres (5 feet) tall, thriving anywhere that has seen recent soil disturbance. Despite being regarded by many as a ‘weed’, growing on waste ground, it has a fascinating biology and history.
Belonging to the Mignonette family, which includes garden plants of the same name, it has a tall spike of small yellow-green flowers. Like Foxgloves it is biennial, flowering in the second year, and starts from the lower flowers, moving upwards over several weeks. When the top flower buds open, the lowermost are already in fruit. This long flowering period thereby increases the chance of pollination by bumblebees and other insects. It is not native but was brought to the UK from continental Europe probably in pre-Roman times, for the purpose of dyeing. Hence its alternative name of Dyer’s Rocket, making reference to its tall spike of flowers. Together with Woad (Isatis tinctora) and Madder (Rubia tinctorium) it constitutes the most common plants used to dye cloth. All are ancient introductions or archaeophytes, Woad a member of the cabbage family, and Madder the bedstraws.
Weld stems, leaves and flowers produce a yellow dye, Woad blue and the root of Madder red. By a process of over-dyeing, it was possible to produce all the colours of the spectrum: woad and weld for green, woad and madder for purples and browns, and weld and madder for orange. Lincoln green produced by over-dyeing was said to be the colour worn by Robin Hood and his merry men. Extracting the dyes is complex and beyond this article, but when used with a mordant such as alum, made the cloth or wool colourfast. Woad as a blue dye was surpassed by indigo from India once the maritime trade routes were established in the 16th. century. All three natural plant-based dyes ceased to be of commercial importance following the discovery and manufacture of cheaper synthetic aniline dyes in the late 19th century.
I am glad to say the story doesn’t end there, as all three ancient plant-based natural dyes are now undergoing a revival, if only on a small scale .
Neither did my encounter with Weld. Travelling home after our Washburn walk, I stopped in Otley and investigated the waste ground next to the newly built Wharfeside care home in Westgate. It may look like a large patch of weeds to most people, but for any botanist, it is a botanical garden waiting to be explored. Yes, and you guessed it, growing and standing proud is Weld or Dyer’s Rocket – waiting for take-off.