Gaelic – Glas lus

Other names:  dyer’s woad, glastum, Asp of Jerusalem 

Easily grown biennial plant which self-seeds. Member of the Brassica family

Native to the steppes and deserts of the Caucasus, Central Asia to Eastern Siberia and western Asia

Woad seeds have been found in neolithic archaeological sites and in an iron age pit in Lincolnshire. Impressions of woad seeds were found on bronze-age pottery from Germany. The ancient Egyptians used woad-dyed cloth to wrap mummies. Julius Caesar reported that the Britanni used to colour their bodies blue with vitrum – possibly translated as woad – either painted or tattooed. The word Picts (picti ) means ‘painted ones’. Gorm ceilteach – celtic blue is a shade of blue..

 If woad was growing in Scotland prior to Roman times it is likely that the seeds had been brought as trade goods.

Woad based pigments were used in the Lindisfarne gospels (around 720). Viking age excavations in York found a dye shop with remains of woad. Traces of indigotin have been found on British textiles from 9th – 11th centuries. Despite the importance of woad as the only source of blue dye in medieval times, in the 12th century the Merchant Guild of Edinburgh specifically excluded those with ‘blue nails’ – an occupatonal hazard of dyeing with woad. An important medieval trade item, grown in England, Holland, Germany and France. When tropical Indigofera (which contains up to 30 times more pigment) started to be imported in the 17th century, Woad continued to be used for some time as a ‘ground’ or base dye to be overdyed with the (probably more expensive) Indigofera and other dyes. It was also used as a reducing agent in the fermentation of indigo. Both were eventually largely replaced in the late 19th century by synthetic dyes.

There are records from 1756 that a prize was given to a dyster in Haddington for producing the greatest quantity of ‘dressed and cured’ woad ‘not under 50 pounds weight’ and in the 1791 Statistical Account of Scotland reference to woad being grown around Haddington, ‘only sufficient for their own use’.

Used in traditional western and Chinese medicine

Gorm ceilteach – celtic blue is a shade of blue..

Dye: an important source of blue dye – one of the three ‘grands teints’. Woad produces the same isatin - the precursor to indigo -  found in Indigofera and Japanese indigo plants, but in smaller quantities. The dyeing process for true blue is more complex than for most natural dyes. A second pigment giving a pink dye can be extracted from the leaves after the indigotin (blue) has been extracted. A much simpler method of extraction, simply rubbing torn leaves with salt, gives a pleasant teal shade on silk.

Overdyeing woad-dyed fibre with other dyes gives other colours – weld (yellow) on woad gives green, madder (red) on woad gives purple etc. Thus the three ‘grands teints’ dyes can be used to produce a wide range of colours.