The Itinerant Flora of a City

Every year the cityscape of Newcastle changes, as old buildings are demolished and the legacy of polluting industries from the past is cleared away. This site is in the Lower Ouseburn valley, once the location of a devil's caudron of industrial pollution but soon to become the site of 76 energy efficient 'green' homes. 

The patch of land in this picture has been derelict for several years - just a pile of broken bricks and earth bulldozed and then left, so that temporary colonisers took over.

Two years after the land was bulldozed, in the summer of 2011, it hosted the finest display of dyers rocket aka weld Reseda luteola that I've ever seen.

The site was so densely covered with this bee-friendly biennial that I wondered whether it might be the legacy of these plants being used in dye production in the 19th. century; in his New Naturalist book Weeds and Aliens Sir Edward Salisbury suggests that the plant's abundance and distribution often suggests that large populations are relicts of the plants' former cultivation. They have a vast seed output (Salisbury quotes up to 76,000 seeds per plant) and it's possible that the seed could have remained dormant for many decades.

There was also a good display of corn poppies amongst this temporary urban field of wild flowers. Their seeds germinate in even the smallest area of waste ground in Newcastle when they are brought to the surface by soil disturbance and exposed to light and moisture. 

Now that the site has been levelled and the rubble taken away, these plants will be on the move again - carried as seeds in rock, bricks and soil that have been taken away and probably used at another site in another part of Newcastle - part of the itinerant flora of the city.

To dye for...

This rather attractive plant is wild mignonette Reseda lutea, a close relative of the cultivated and fragrant mignonette R.odorata that used to be a common feature of cottage gardens but seems to be rarely grown these days. Wild mignonette’s flowers are a magnet for bees, which makes it a good plant for a wildlife garden, but its coarser and much larger cousin dyers rocket Reseda luteola, which I found growing beside it on some waste ground on the Durham coast, is in many ways more interesting.

Unlike mignonette, dyer’s rocket, also known as weld, contains a flavonoid compound called luteolin which is a bright yellow dye that has been used in the past for colouring cotton and wool. According to the Roman writer Pliny it was the preferred dye for clothes of fashionable ladies and was used to colour wedding garments and the robes of vestel virgins.

The 18th. century botanist William Withering wrote an enthusiastic account of the plant’s properties as a source of yellow dye. In his day it was also known as yellow-weed or dyer’s luteola. “This plant affords a most beautiful yellow dye for cotton, woollen, mohair, silk and linen, and is constantly used by the dyers for that purpose”, he wrote in his Botanical Arrangement of 1776. “Blue cloths dipped in a decoction of it become green. The yellow colour of the plant called Dutch Pink, is got from this plant. The tinging quality resides in the stems and roots, and it is cultivated in sandy soils, rich soils making the stalk hollow and not so good”. Nearly a century later Dutch Pink paint was still used by watercolourists, mentioned by C. Pierpoint Johnson when he wrote about the virtues of dyer's rocket in his Useful Plants of Great Britain: A Treatise, published in 1863. He observed that “it is now much grown in Essex, and in some districts of Yorkshire, being sown in April or May, and pulled up when nearly out of flower and dried in the sun". He observed that the dye was particularly concentrated in the seed but was “always liable to fade in sunlight”. Given the plant's attraction for bees, a field of dyer's rocket must have positively hummed with these insects. Being a biennial, the species would have taken two years to produce a usable crop. These day's it's a common plant of waste ground, often around habitation, so I wonder how much of its distribution is natural and how much is a legacy of past cultivation? In his book Weeds and Aliens, published in 1961, Sir Edward Salisbury mentions that the plant commonly sets as many as 76,000 seeds and that these may have prolonged dormancy. He quotes a letter to the Times in 1931 claiming that dyer's rocket seeds germinated after the Roman vallum at Cirencester was excavated by archaeologists, leading him to posit that "these arose from seed over 1800 years old is therefore not incredible" - though surely unlikely, although it is very tempting to speculate that these might have been progeny of plants grown by the Romans to provide yellow dye for wedding dresses. 

The plant itself seems to have an affinity with the sun and in Dye Plants and Dyeing by John and Margaret Cannon (2002) there is an intriguing mention of the way in which the inflorescence tips bend towards the sun (as they are doing in the picture here) and follow it on its passage across the sky. So what happens when darkness falls - do they bend back to point westwards in anticipation of sunrise? Apparently not. They mention that the great botanist and taxonomist Linnaeus was curious to find out what happened too and went to look at the plant at midnight, when he found that all the inflorescences pointed northwards. He was working in sub-Arctic regions and it seems from their account that in the high latitudes up there, in the land of the midnight sun, the infloresecence tips just followed the sun during its continued 24 hr. passage around the sky in summer and didn't 'unwind' and return to point westward - although it isn't absolutely clear from their account that this was the case.

John and Margaret Cannon (2002) Dye Plants and Dyeing. A&C Black, in association with the Royal Botanic Gardens, Kew.

C. Pierpoint Johnson (1863) The Useful Plants of Great Britain: A Treatise. Published by Robert Hardwickw, 192, Picadilly, London.

 

Sir Edward Salisbury (1961) Weeds and Aliens. Collins New Naturalist no. 43.

 

William Withering (1776) Botanical Arrangement of all the Vegetables Naturally Growing in Great Britain.