Plant use as dyes

Plant use as Dyes

In the summer months our gardens are full of colourful flowers which give us pleasure and provide nectar for bees and other pollinators.

Colours exist in plants due to the many thousands of different pigments that plants produce as they grow. The pigments developed to act as visible signs to attract insects, birds and mammals for pollination and to protect the plant from damage by UV and visible light. Photosensitive cells in the human retina allow the brain to perceive the reflected wavelengths from the pigments as colour. Thus, a yellow flower for instance, is only recognised as yellow because all the other lightwaves have been absorbed. Bee’s eyes are able to detect ultraviolet light. Some signs of nectar on flowers are only visible in ultraviolet light and it is thought that the ability to see ultraviolet light helps them navigate on cloudy days.

The pigments found in plants, lichen, fungi and in the earth were used exclusively until the first synthetic dye was stumbled upon in 1856 by Henry Perkin when researching coal tar for a substitute for quinine which was used to treat malaria.

Many pigments cannot be extracted from plant material or are unstable when applied to fibres, are not lightfast, or do not bind to the fibre even with the use of mordant or fixatives. As a general rule, plants that were historically successful for dyeing have “Dyer’s” in their common name or “tinctoria” in the Latin name. Dyer’s Chamomile, Anthemis tinctoria and Dyer’s Coreopsis, Coreopsis tinctoria both produce a yellow dye. The roots of Madder, Rubia tinctoria produces a red dye, whilst Japanese Indigo, Persicaria tinctoria and Indigo Indigofera tinctoria unsurprisingly, produce blue dyes.

Photos
Right: Coreopsis tinctoria
Below Left: Rubia tinctoria
Below Right: Indigofera tinctoria

However, there are many more that are not acknowledged as dye plants by their botanical names. Many dye plants have simple flowers which are beneficial to bees because the nectar is easily accessible. Other plants that readily produce dyes, such as Calendula and Lavender, also have uses in herbal medicine or cosmetics. It is not just humans that benefit from the additional properties that dye plants have. The many varieties of oak tree are well documented as providing a home to hundreds of life forms and produce tannins in their bark, oak galls can be used to make ink. Ivy flowers are the main food of the Ivy Bee, Colletes hederae - a fairly new species in the UK. The plants provide shelter for insects and small mammals, the berries provide food for birds and a green dye can be extracted from them.

Locally, two plants have been of significant importance; Dyer’s Woad, also known as Glastum, Isatis tinctoria was a hugely important crop throughout Somerset. Glastonbury also means “the place where Woad grows". It is a very hungry plant and only develops the dye in the second year. So much land was used for and degraded by the production of Woad that it is thought to have been the cause of famine in 1586. Despite Woad being so widely grown it rarely appears in the wild and in 2014 was thought to have disappeared from the only spot where it had been present for 200 years, in Tewkesbury.

The other plant that has huge significance to Keynsham is Haematoxylum campechianum, Blood tree or Logwood bark was imported from South America and ground up in Albert Mill, St Clements Road. Logwood produces colours from purple to black depending on how it is processed. The mill was still operating until 1964.

Julia Shahin, August 2021