Indigo is among the oldest dyes to be used for textiles. Its use dates back to the 7th century BC. A variety of plants produce indigo dye, but the most commonly used, because it has a high concentration of indigo is indigofera tinctoria.
Woad was used in Europe, as it is better suited to the climate, It yields the same dye substances but at lower concentration, producing beautiful soft blues. Nowadays, synthetic indigo is often used instead of the plant varieties.
I use indigo and woad in conjunction with ecoprinting and also using ancient Japanese shibori techniques, where stititching and clamping are used to reserve parts of the cloth, leaving a white pattern against the blue