Woad is the common name of Isatis tinctoria. In Medieval Europe it was the only source of blue dye for textiles. The leaves of the woad plant contain the same dye molecule as Indigofera tinctoria, although in much weaker concentration and needing a different extraction process. This makes colouring with woad a more subtle and delicate art. The same recipes used for indigo may be used for woad. The shades obtained from woad are slightly different and call to mind the areas where it was most popular - the south of France.