| |
|
Until the 17th century woad and indigo were the only blue dyes available in Europe and Asia. The blue pigment in woad is the same as in indigo dye, but the concentration of the pigment is greater in indigo. Laws were passed in some parts of Europe to protect the woad industry from the competition of the indigo trade. With the development of a chemical process to synthesize the pigment, both the woad and natural indigo industries collapsed in the first years of the twentieth century. The last commercial harvest of woad occurred in 1932, in Lincolnshire, England.
Formerly cultivated, Isatis tinctoria is now viewed as a noxious weed in many placed in the United States.