View source for Isatis tinctoria

{{Short description|Species of flowering plant}}
{{Redirect|Woad|the American radio station|WOAD (AM)|'Woads' as a fictional name for a tribe|Picts in literature and popular culture}}
{{Redirect|Vitrum|the genus of tunicates|Vitrum (tunicate)}}
{{Speciesbox
|image = Isatis tinctoria02.JPG
|image_caption = Woad flowers
|genus = Isatis
|species = tinctoria
|authority = [[Carl Linnaeus|L.]]
|synonyms = {{ubl|''Isatis indigotica'' {{small|Fortune}}|''Isatis japonica'' {{small|Miq.}}}}
}}

[[File:Isatis tinctoria (s. str.) sl5.jpg|thumb|Woad plants]]
[[File:Isatis tinctoria MHNT.BOT.2011.3.12.jpg|thumb|Fruits of ''Isatis tinctoria'']]
'''''Isatis tinctoria''''', also called '''woad''' ({{IPAc-en|ˈ|w|oʊ|d}}), '''dyer's woad, dyer's-weed''', or '''glastum''', is a [[flowering plant]] in the family [[Brassicaceae]] (the mustard family) with a documented history of use as a blue dye and medicinal plant. 

Its genus name, ''Isatis'', derives from the ancient Greek word for the plant, {{lang|grc|ἰσάτις}}. It is occasionally known as '''Asp of Jerusalem'''. Woad is also the name of a blue [[dye]] produced from the leaves<ref>
{{cite web
 | url         = http://www.merriam-webster.com/dictionary/woad
 | title       = Woad – Definition and More
 | access-date  = 3 February 2011
 | publisher   = Merriam Webster
}}
</ref> of the plant. Woad is native to the [[steppe]] and desert zones of the [[Caucasus]], Central Asia to Eastern [[Siberia]] and [[Western Asia]]<ref>{{cite book |last=Hegi |first=Gustav |title=Illustrierte Flora von Mitteleuropa. Spermatophyta, Band IV Teil 1. Angiospermae, Dicotyledones 2 |pages=126–131 |date=1986}}</ref> but is now also found in South-Eastern and Central [[Europe]] and western [[North America]].

Since ancient times, woad was an important source of blue dye and was cultivated throughout Europe, especially in Western and Southern Europe. In medieval times, there were important woad-growing regions in England, Germany and France. Towns such as [[Toulouse]] became prosperous from the woad trade. 

Woad was eventually replaced by the more colourfast ''[[Indigofera tinctoria]]'' and, in the early 20th century, both woad and ''Indigofera tinctoria'' were replaced by synthetic blue dyes. Woad has been used medicinally for centuries. The double use of woad is seen in its name: the term ''Isatis'' is linked to its ancient use to treat wounds; the term ''tinctoria'' references its use as a dye.<ref>{{Cite journal |last1=Speranza |first1=Jasmine |last2=Miceli |first2=Natalizia |last3=Taviano |first3=Maria Fernanda |last4=Ragusa |first4=Salvatore |last5=Kwiecień |first5=Inga |last6=Szopa |first6=Agnieszka |last7=Ekiert |first7=Halina |date=2020-03-01 |title=Isatis tinctoria L. (Woad): A Review of Its Botany, Ethnobotanical Uses, Phytochemistry, Biological Activities, and Biotechnological Studies |journal=Plants |volume=9 |issue=3 |pages=298 |doi=10.3390/plants9030298 |issn=2223-7747 |pmc=7154893 |pmid=32121532|doi-access=free }}</ref> There has also been some revival of the use of woad for craft purposes.<ref>{{Cite web|url=https://folkcraftrevival.com/everything-you-need-to-know-about-dyers-woad/|title = Natural Dyeing using Dyer's Woad|date = 13 December 2018}}</ref>

==History of woad cultivation==
===Ancient use===

The first archaeological finds of woad seeds date to the [[Neolithic]] period. The seeds have been found in the cave of l'Audoste, [[Bouches-du-Rhône]], France. Impressions of seeds of ''Färberwaid'' (Isatis tinctoria L.) or German indigo, of the plant family ''Brassicaceae'', have been found on pottery in the [[Iron Age]] settlement of [[Heuneburg]], Germany. Seed and pod fragments have also been found in an Iron Age pit at Dragonby, North Lincolnshire, United Kingdom.<ref name="Van Der Veen">{{Cite journal|last1=Van Der Veen|first1=M.|last2=Hall|first2=A. R.|last3=May|first3=J.|date=1993-11-01|title=Woad and the Britons Painted Blue|journal=Oxford Journal of Archaeology|language=en|volume=12|issue=3|pages=367–371|doi=10.1111/j.1468-0092.1993.tb00340.x|issn=1468-0092}}</ref> The [[Hallstatt]] burials of the [[Hochdorf Chieftain's Grave]] and [[Hohmichele]] contained textiles dyed with woad.

Melo and Rondão write that woad was known "as far back as the time of the ancient Egyptians, who used it to dye the cloth wrappings applied for the mummies."<ref>{{cite journal |first1=J. Sérgio Seixas |last1=de Melo |first2=Raquel |last2=Rondão |first3=Hugh D. |last3=Burrows |first4=Maria J. |last4=Melo |first5=Suppiah |last5=Navaratnam |first6=Ruth |last6=Edge |first7=Gundula |last7=Voss |title=Spectral and Photophysical Studies of Substituted Indigo Derivatives in Their Keto Forms |journal=ChemPhysChem |volume=7 |issue=11 |pages=2303–2311 |date=November 13, 2006 |doi=10.1002/cphc.200600203|pmid=17009279 |hdl=10316/8269 |hdl-access=free }}</ref> Skelton states that one of the early dyes discovered by the ancient Egyptians was "blue woad (Isatis tinctoria)."<ref>{{cite journal |first=Helen |last=Skelton |title=A colour chemist's history of Western art |journal=Review of Progress in Coloration and Related Topics |volume=29 |date=1999 |pages=43–64 |doi=10.1111/j.1478-4408.1999.tb00127.x |doi-access=free}}</ref> Lucas writes, "What has been assumed to have been Indian Indigo on ancient Egyptian fabrics may have been woad."<ref>{{cite book |first=Alfred |last=Lucas |title=Ancient Egyptian Materials and Industries |publisher=E. Arnold & Company |location=London |date=1934 |url=https://archive.org/details/b29828739 |edition=2nd |page=[https://archive.org/details/b29828739/page/314 314]}}</ref> Hall states that the ancient Egyptians created their blue dye "by using indigotin, otherwise known as woad."<ref>{{cite book |first=Rosalind |last=Hall |title=Egyptian Textiles |series=Shire Egyptology |page=10 |date=2008 |publisher=Bloomsbury Publishing PLC |isbn=9780852638002}}</ref>

A dye known as {{langx|arc|סטיס|satis|label=none}} in [[Aramaic language|Aramaic]], is mentioned in the Babylonian [[Talmud]].<ref>{{Cite Talmud|b|Shabbat||68a}}</ref><ref>{{Cite Talmud|b|Shabbat||79a}}</ref><ref>{{Cite Talmud|b|Shabbat||90a}}</ref><ref>{{Cite Talmud|b|Pesachim||56b}}</ref><ref>{{Cite Talmud|b|Megillah||24b}}</ref>

Celtic blue is a shade of blue, also known as {{lang|cy|glas celtig}} in [[Welsh language|Welsh]], or {{lang|ga|gorm ceilteach}} in both the [[Irish language]] and in [[Scottish Gaelic]]. Julius Caesar reported (in {{lang|la|[[Commentarii de Bello Gallico]]}}) that the Britanni used to colour their bodies blue with {{lang|la|vitrum}}, a word that means primarily {{gloss|glass}}, but also the domestic name for the woad (''Isatis tinctoria''), besides the [[Gaulish]] loanword {{lang|la|glastum}} (from  [[Proto-Celtic]] {{lang|cel-x-proto|*glastos}} {{gloss|green}}). The connection seems to be that both glass and the woad are "water-like" ({{langx|la|vitrum}} is from [[Proto-Indo-European]] ''{{PIE|*wed-ro-}}'', {{gloss|water-like}}).<ref>Entry "vitrum", in: Michiel de Vaan (ed.), ''Etymological Dictionary of Latin'' (Ph. D. 2002). First published online at Brill, October 2010. Consulted online on 23 May 2019.</ref> In terms of usage, the Latin {{lang|la|vitrum}} is more often used to refer to glass rather than woad.<ref name="Finlay">{{Cite book|first=Victoria |last=Finlay|title=Color: A Natural History of the Palette|date=2004|publisher=Random House Trade Paperbacks|isbn=9780812971422|edition=Later Printing|location=New York|language=en}}</ref> The use of the word for the woad might also be understood as "coloured like glass", applied to the plant and the dye made from it.

Gillian Carr conducted experiments using indigo pigment derived from woad mixed with different binders to make body paint. The resulting paints yielded colours from "grey-blue, through intense midnight blue, to black".<ref name="Carr 277">{{Cite journal|last=Carr|first=Gillian|date=2005-08-01|title=Woad, Tattooing and Identity in Later Iron Age and Early Roman Britain|journal=Oxford Journal of Archaeology|language=en|volume=24|issue=3|page=277|doi=10.1111/j.1468-0092.2005.00236.x|issn=1468-0092}}</ref><!-- This is obviously based on [[False etymology|paretymological]] assumptions: Carr suggests the translation of: "dye themselves with [[Glaze (painting technique)|glazes]]" or "'infect themselves (or 'work into themselves') with glass'".  The latter could refer to using glass in the [[Tattooing|tattooing process]] or to scarification. --> People with modern experiences with woad as a tattoo pigment have claimed that it does not work well, and is actually [[Corrosive substance|caustic]] and causes scarring when put into the skin.<ref name="problem">{{cite web |url=http://www.dunsgathan.net/essays/woad.htm |title=The Problem of the Woad |work=Dunsgathan.net |first=Saigh Kym |last=Lambert |date=2004 |access-date=2012-10-09}}</ref>{{efn|Compare Pat Fish, quoted in ''Woad and its Mis-Association with Pictish Body Art'': "[Woad] is also an amazing astringent. The tattoo I did with it literally burned itself to the surface, causing me to drag the poor experimented-upon fellow to my doctor who gave me a stern chastizing for using {{sic|nolink=y|innap|propriate}} ink. It produced quite a bit of scar tissue, but healed very quickly, and no blue was left behind. This leads me to think it may have been used for closing battle wounds. I believe the Celts used copper for blue tattoos, they had plenty of it, and soot ash cardon for black. Unfortunately we need more bog bodies to prove this point!"<ref>{{cite web |url= http://www.hippy.com/albion/woad.htm |access-date=2014-11-13 |archive-url=https://web.archive.org/web/20050608074604/http://www.hippy.com/albion/woad.htm |archive-date=2005-06-08 |url-status=usurped |title=Woad and {{as written|i|t's [sic]}} mis-association with Pictish BodyArt |website=Modern Hengineering}}</ref>}}

It has also been claimed that Caesar was referring to some form of [[copper]]- or [[iron]]-based pigment.<ref name="Van Der Veen" /> Analysis done on the [[Lindow Man]] did return evidence of copper. The same study also noted that the earliest definite reference to the woad plant in the British Isles dates to a seed impression on an Anglo-Saxon pot. The authors theorize that vitrum could have actually referred to [[copper(II) sulfate]]'s naturally occurring variant [[chalcanthite]] or to the mineral [[azurite]].<ref>{{Cite journal|last1=Pyatt|first1=F.b.|last2=Beaumont|first2=E.h.|last3=Lacy|first3=D.|last4=Magilton|first4=J. R.|last5=Buckland|first5=P. C.|date=1991-03-01|title=Non Isatis Sed Vitrum or, the Colour of Lindow Man|journal=Oxford Journal of Archaeology|language=en|volume=10|issue=1|pages=61–73|doi=10.1111/j.1468-0092.1991.tb00006.x|issn=1468-0092}}</ref> A later study concluded the amount was "not of sufficient magnitude to provide convincing evidence that the copper was deliberately applied as paint".<ref>M. R. Cowell, P. T. Craddock (1995), "Addendum: Copper in the Skin of Lindow Man", ''Bog Bodies: New Discoveries and New Perspectives,'' British Museum Press, p. 74 f. {{ISBN|0-7141-2305-6}}.</ref>

Woad was an important dyeing agent in much of Europe and parts of England during the medieval period. However, dye traders began to import [[indigo]] during the sixteenth and seventeenth centuries, which threatened to replace locally grown woad as the primary blue dye.<ref name="Finlay" /> The translation of vitrum as woad may date to this period.<ref>{{cite book |first=Joan |last=Thirsk |chapter=The agricultural landscape: fads and fashions |editor-first=S. R. J. |editor-last=Woodell |title=The English Landscape Past, Present and Future |publisher=[[Oxford University Press]] |date=1985 |pages=[https://archive.org/details/englishlandscape0000wood/page/129 129]–147 |isbn=978-0-19-211621-5 |url=https://archive.org/details/englishlandscape0000wood |url-access=registration}}</ref>

===Medieval period onwards===
[[File:The hunt of the unicorn6.jpg|thumb|right|The tapestry series ''[[The Hunt of the Unicorn]]'' (here No.&nbsp;6: ''The Unicorn is Killed and Brought to the Castle'', {{circa|1500}}), was dyed with [[Reseda luteola|weld]] (yellow), [[Rubia|madder]] (red), and [[woad]] (blue).]]

Woad was one of the three staples of the European dyeing industry, along with [[Reseda luteola|weld]] (yellow) and [[Rubia|madder]] (red).<ref name=indigo>{{cite book|last=Balfour-Paul|first=Jenny|title=Indigo|year=2006|publisher=Archetype Publications|location=London|isbn=978-1-904982-15-9}}</ref> [[Chaucer]] mentions their use by the dyer ("litestere") in his poem ''The Former Age'':<ref>{{cite book |url=http://www.bartleby.com/258/62.html |section=The Former Age |via=Bartleby.com |editor-first=Walter W. |editor-last=Skeat |title=The Complete Poetical Works of Geoffrey Chaucer |first=Geoffrey |last=Chaucer |date=1894}}</ref>

[[File:Schreber woad mill 1752.JPG|thumb|left|Illustration of German woad mill in Thuringia, 1752.]]
[[File:Pastel pigment cocagnes et feuilles - Muséum du pastel.jpg|thumb|left|Steps of the leaves to the blue dye.]]

:::No mader, welde, or wood no litestere
:::Ne knew; the flees was of his former hewe;

The three colours can be seen together in tapestries such as ''[[The Hunt of the Unicorn]]'' (1495–1505), though typically it is the dark blue of the woad that has lasted best. Medieval uses of the dye were not limited to textiles. For example, the illustrator of the ''[[Lindisfarne Gospels]]'' ({{circa|720}}) used a woad-based pigment for blue paint. As does the late 13th century North Italian manual on [[Illuminated manuscript|book illumination]] ''[[Liber colorum secundum magistrum Bernardum]]'' describe its usage.

In [[Viking Age]] levels at archaeological digs at [[York]], a dye shop with remains of both woad and [[Rubia|madder]] have been excavated and dated to the 10th century. In medieval times, centres of woad cultivation lay in [[Lincolnshire]] and [[Somerset]] in England, [[Jülich]] and the [[Erfurt]] area in [[Thuringia]] in Germany, [[Piedmont (Italy)|Piedmont]] and [[Tuscany]] in Italy, and [[Gascony|Gascogne]], [[Normandy]], the [[Somme River|Somme Basin]] (from [[Amiens]] to [[Saint-Quentin, Aisne|Saint-Quentin]]), [[Brittany (administrative region)|Brittany]] and, above all, [[Languedoc]] in France. This last region, in the triangle created by [[Toulouse]], [[Albi]] and [[Carcassonne]], known as the [[Lauragais]], was for a long time the biggest producer of woad, or ''pastel'', as it was locally known. One writer commented that "woad […] hath made that country the happiest and richest in Europe."<ref name="indigo"/>

<!-- [[File:Lycee-Fermat 15.JPG|thumb|Woad merchant [[Hôtel de Bernuy|Jean de Bernuy's 16th-century mansion]] in [[Toulouse]]]] -->
[[File:Bachelier - Hôtel d'Assézat - Toulouse - La cour d'honneur.jpg|thumb|Woad merchant [[Hôtel d'Assézat|Pierre Assézat's 16th-century mansion]] in [[Toulouse]].]]

The prosperous woad merchants of [[Toulouse]] displayed their affluence in splendid mansions, many of which still stand, as the [[Hôtel de Bernuy]] and the [[Hôtel d'Assézat]]. One merchant, Jean de Bernuy, a Spanish Jew who had fled the [[Spanish Inquisition]], was credit-worthy enough to be the main guarantor of the ransomed King [[Francis I of France|Francis I]] after his capture at the [[Battle of Pavia]] by [[Charles V, Holy Roman Emperor|Charles V of Spain]].<ref name="indigo"/> Much of the woad produced here was used for the cloth industry in southern France,<ref>{{cite book|first1=Michael |last1=Pauls |title=Gascony & the pyrenees |year=2007 |publisher=Cadogan Guides |location=London |isbn=978-1-86011-360-4 |edition=5th |first2=Dana |last2=Facaros |page=314}}</ref> but it was also exported via [[Bayonne]], [[Narbonne]] and [[Bordeaux]] to Flanders, the Low Countries, Italy, and above all Britain and Spain.

After cropping the woad eddish could be let out for grazing sheep.<ref>{{cite news|url=https://www.britishnewspaperarchive.co.uk/viewer/bl/0000237/17891113/021/0002?noTouch=true|title=Keeping for sheep|newspaper=Stamford Mercury|date=13 November 1789|url-access=limited}}</ref>
The woad produced in Lincolnshire and Cambridgeshire in the 19th century was shipped out from the [[Port of Wisbech]],<ref>{{cite news|title=Shipping News|newspaper=Stamford Mercury|date= 11 April 1788}}</ref> [[Spalding, Lincolnshire|Spalding]] and [[Boston, Lincolnshire|Boston]],<ref>{{cite news|title=Boston Ship News|newspaper=Stamford Mercury|date=6 April 1792}}</ref> both the last to northern mills and the USA. The last portable woad mill was at [[Parson Drove]], Cambridgeshire, [[Wisbech & Fenland Museum]] has a woad mill model, photos and other items used in woad production.<ref>{{cite journal|last=Monger|first=Garry|title=Woad in the fens|journal=The Fens & Surrounding|volume=12|page=16|year=2019}}</ref>
A major market for woad was at [[Görlitz]] in Lausitz.<ref>{{cite book |first=Werner |last=Sombart |title=Der moderne Kapitalismus |edition=15th |date=1928 |volume=1 |page=[https://archive.org/details/dermodernekapita11somb/page/231 231] |publisher=München, Leipzig, Duncker & Humblot |url=https://archive.org/details/dermodernekapita11somb |url-access=registration |language=de}}</ref> The citizens of the five Thuringian ''Färberwaid'' (dye woad) towns of [[Erfurt]], [[Gotha (town)|Gotha]], [[Tennstedt]], [[Arnstadt]] and [[Langensalza]] had their own charters. In Erfurt, the woad-traders gave the funds to found the [[University of Erfurt]]. Traditional fabric is still printed with woad in Thuringia, [[Saxony]] and [[Lusatia]] today: it is known as ''Blaudruck'' (literally, "blue print(ing)").

In the Marche region, the cultivation of the plant was an important resource for the [[Duchy of Urbino]] in Italy. To fully understand the importance of the ford industry in the State of [[Urbino]], it is enough to read the comprehensive Chapters of the art of wool in 1555, which dictated prescriptions regarding the cultivation and trade of woad, whether in loaves or macerated (powdered).<ref>G. Luzzatto - Notizie e documenti sulle arti della lana e della seta in Urbino "Le marche" VII 1907 p.p. 185-210</ref> Testifying to the importance that this crop had in the economy in addition to the archival documents was the identification of a hundred millstones surveyed by Delio Bischi in the province of Pesaro and Urbino, the original use of which had become completely unknown as their memory had been lost.<ref>Delio Bischi - Convegno internazionale sul Guado, Erfurt (Turingia) 3-7 Giugno 1992, Estratto da Esercitazioni dell’Accademia Agraria di Pesaro Serie 3ᵃ – Volume 24°- Anno 1992</ref>

===Use as Chinese medicine===
{{See also|Chinese traditional medicine}}
The woad plant's roots are used in [[Traditional Chinese medicine]] to make a medicine known as ''banlangen'' ({{transl|cmn|bǎnlán'gēn}} {{lang|zh|板蓝根}}) that purports to have antiviral properties.<ref>{{cite journal |last1=Yu |first1=B |last2=Lin |first2=F |last3=Ning |first3=H |last4=Ling |first4=B |title=Network pharmacology study on the mechanism of the Chinese medicine Radix Isatidis (Banlangen) for COVID-19. |journal=Medicine |date=13 August 2021 |volume=100 |issue=32 |pages=e26881 |doi=10.1097/MD.0000000000026881 |pmid=34397905 |pmc=8360416 }}</ref> ''Banlangen'' is used as an herbal medicinal tea in China for colds and tonsillar ailments. Used as a tea, it has a brownish appearance and (unlike most Chinese medicines) is mildly sweet in taste.

==Woad and indigo==
[[File:Isatis tinctoria 003.JPG|thumb|upright=0.8|Indigo extracted from woad]]
{{Infobox color
| title=Celtic Blue
| hex=246bce
| spelling=colour
| source=[https://www.google.co.uk/search?q=celtic+blue&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi95M2Hz6bWAhXFvBoKHTzlDOQQ_AUICigB&biw=1024&bih=679#imgrc=u9QI8GmuiEZTzM: Internet]}}

The dye chemical extracted from woad is [[indigo dye|indigo]], the same dye extracted from "true indigo", ''[[Indigofera tinctoria]]'', but in a lower concentration.  Following the [[Portuguese discovery of the sea route to India]] by the navigator [[Vasco da Gama]] in 1498, great amounts of indigo were imported from Asia. Laws were passed in some parts of Europe to protect the woad industry from the competition of the indigo trade. It was proclaimed that indigo caused yarns to rot.<ref>{{cite magazine |url=http://www.gutenberg.org/files/13242/13242-8.txt |magazine=Lippincott's Magazine of Popular Literature and Science |volume=17 |issue=100 |date=April 1876 |title=Sketches of India |via=Project Gutenberg}}</ref> This prohibition was repeated in 1594 and again in 1603.<ref>D G Schreber, ''Historische, physische und economische Beschreibung des Waidtes'', 1752, the appendix; Thorpe JF and Ingold CK, 1923, ''Synthetic colouring matters - vat colours'' (London: Longmans, Green), p. 23</ref> In France, [[Henry IV of France|Henry IV]], in an edict of 1609, forbade under pain of death the use of "the false and pernicious Indian drug".<ref>{{cite book |first=Édouard |last=Foucaud |editor-last=Frost |editor-first=John |title=The book of illustrious mechanics |publisher=D. Appleton |year=1846 |page=[https://archive.org/details/bookillustrious00foucgoog/page/n246 236] |url=https://archive.org/details/bookillustrious00foucgoog}}</ref>

With the development of a chemical process to [[Indigo dye#Era of synthetic indigo|synthesize]] the pigment, both the woad and natural indigo industries collapsed in the first years of the 20th century. The last commercial harvest of woad until recent times occurred in 1932, in [[Lincolnshire]], Britain. Small amounts of woad are now grown in the UK and France to supply craft dyers.<ref>{{cite web|first=Chris|last=Cooksey |url-status=dead |url=http://www.chriscooksey.demon.co.uk/indigo/woad.html |title=Indigo - woad |publisher=Chris Cooksey |access-date=2012-10-09 |archive-date=2012-02-19 |archive-url=https://web.archive.org/web/20120219063526/http://www.chriscooksey.demon.co.uk/indigo/woad.html }}</ref> The classic book about woad is ''The Woad Plant and its Dye''<ref>{{cite book|last=Hurry|first=Jamieson Boyd|editor-last= Milford|editor-first=Humphrey Sumner|editor-link=Humphrey Sumner Milford |title=The Woad Plant and its Dye|year=1930|publisher=[[Oxford University Press]] |location=London|isbn=9780678007792|quote=isbn 1973 reprint |oclc=702743|via=[[Archive.org]] |url=https://archive.org/details/woadplantitsdye0000unse/page/n7/mode/2up |url-access=registration }}</ref> by J. B. Hurry, Oxford University Press of 1930, which contains an extensive bibliography.<ref>{{cite web |url=http://www.chriscooksey.demon.co.uk/indigo/jbhurry.html |title=J B Hurry's woad bibliography |publisher=Chris Cooksey |access-date=2012-10-09 |archive-date=2012-04-16 |url-status=dead |archive-url=https://web.archive.org/web/20120416121530/http://www.chriscooksey.demon.co.uk/indigo/jbhurry.html }}</ref>

A method for producing blue dye from woad is described in ''The History of Woad and the Medieval Woad Vat'' (1998) {{ISBN|0-9534133-0-6}}.<ref>{{cite web
| url         = http://www.imperial-purple.com/dyes1.html
| title         = Historic Dyes Series No. 1 - The History of Woad and the Medieval Woad Vat by John Edmonds
| access-date         = 28 January 2011
| publisher         = unknown
| archive-url         = https://web.archive.org/web/20100825034609/http://www.imperial-purple.com/dyes1.html
| archive-date         = 25 August 2010
| url-status         = dead
}}</ref>

Woad is biodegradable and safe in the environment. In Germany, there have been attempts to use it to protect wood against decay without applying dangerous chemicals.<ref>{{Cite patent |status=patent |country=EP |number=1223198A1 |fdate=2001-12-11 |invent1=Hans-Martin Dr. Dahse |invent2=Klausjürgen Dr. Dornberger |invent3=Albrecht Feige |invent4=Dr. Matthias Hilliger, Prof. Waldemar Künkel, Prof. Axel Stelzner |title=Process for the development of an environmentally desirable raw material based on woad (isatis tinctoria L.) |url=https://patents.google.com/patent/EP1223198A1/en |pridate=2000-12-13 |gdate=2004-02-25}}</ref> Production of woad is increasing in the UK for use in [[ink]]s, particularly for [[inkjet printer]]s, and dyes.

==Invasive and noxious weed==
In certain locations, the plant is classified as a non-native and invasive weed. It is listed as a [[noxious weed]] by the agriculture departments of several states in the western United States: Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming.<ref>{{cite web | publisher = USDA Natural Resources Conservation Service | title = Plants Profile for ''Isatis tinctoria'' (Dyer's woad) | url = https://plants.usda.gov/home/plantProfile?symbol=ISTI | access-date = November 11, 2014 |website=USDA Plants Database }}</ref><ref>{{cite web|website=Arizona Department of Agriculture |title=Prohibited, Regulated and Restricted Noxious Weeds |url=http://www.azda.gov/PSD/quarantine5.htm |access-date=November 24, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20091123224508/http://www.azda.gov///PSD/quarantine5.htm |archive-date=November 23, 2009 }}</ref> In Montana, it has been the target of an extensive, and largely successful, eradication attempt.<ref>{{cite journal | url = http://www.weedcenter.org/inv_plant_info/docs/MT-Dyers_woad.pdf | first1 = Monica L. |last1=Pokorny |first2=Jane M. |last2=Krueger-Mangold | title = Evaluating Montana's Dyer's Woad (''Isatis tinctoria'') Cooperative Eradication Project | journal = Weed Technology |date=2007 |volume=21 |issue=1 |pages=262–269 | url-status = dead | archive-url = https://web.archive.org/web/20110104215421/http://www.weedcenter.org/inv_plant_info/docs/MT-Dyers_woad.pdf | archive-date = 2011-01-04 |doi=10.1614/WT-06-048.1 | s2cid = 55153477 }}</ref>

==Notes==
{{Notelist}}

==References==
{{Reflist|25em}}

===Sources===
* {{cite book |first=Renate |last=Kaiser-Alexnat |year=2013 |title=Wonder Woad: Experiences involving human and plant – especially woad – reported in pictures and stories |publisher=epubli GmbH |location=Berlin, DE |isbn=978-3-8442-5590-4 |oclc=923961362}}
* {{cite book|first=Colin|last=Taylor|title=Lauragais: Steeped in History, Soaked in Blood|year=2018|publisher=Troubador Publishing |language=English| isbn=978-1789015836}}

==External links==
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* [http://www.woad.org.uk/ Woad.org.uk - All About Woad - Cultivation, Extraction, Dyeing with Woad, History and facts about woad]
* [http://www.erfurt-guide.de/se2.htm The Former Woad Industry] Rex Wailes in Transactions of the Newcomen Society, 1935-36 Vol 16.
* [https://plants.usda.gov/home/plantProfile?symbol=ISTI USDA information on ''Isatis tinctoria'']

{{Dyeing}}
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[[Category:Brassicaceae]]
[[Category:Flora of Western Asia]]
[[Category:Flora of Siberia]]
[[Category:Medicinal plants of Asia]]
[[Category:Plant dyes]]
[[Category:Medicinal plants of Europe]]
[[Category:Plants used in traditional Chinese medicine]]
[[Category:Plants described in 1753]]
[[Category:Taxa named by Carl Linnaeus]]