Vegetable dyes giving an indigo blue colour have been used extensively in China for centuries but little work has been done on the plants that produce the dye substance, indigotin. Indigo(Lan Dian 蓝靛 in Chinese ) is completely different from other vegetable dyes and can be obtained from a number of plants in different genuses. It is commonly thought polygonum is used in China and the ethnic groups in southwest China may use the indigofera tinctoria that is used by the Hmong in Thailand. During research by the author in Guizhou from 1990 to 1993, a number of plants used by the ethnic groups were identified. In the southeast, southwest and the Dong area, strobilanthes cusia(formerly flaccidifolius), an evergreen shrub propagated by basal cuttings, was found growing and was been soaked in wooden barrels to produce a dye paste. Fresh cuttings of strobilanthes are planted at the beginning of the year to yield rich green leaves that are picked from July to make the indigo paste. Indigofera  was found only  occasionally in the southeast, polygonum tinctoria was found in the southeast but not in the southwest. These plants are difficult to locate--peasant tuck them into small fields between vegetables, rice and other cash crops. Indigo root cuttings are sometimes sold by the Miao at the local markets. Other genuses are seeded.

A dye vat is started from a paste, made from the plants immediately on harvesting, so that indigo dyeing can continue year-round. The paste is made in slightly different ways but a sequence emerged. Leaves of the indigo plant are cut between July and October, and carried down from the peasant's plot in baskets on shoulder poles to handmade wooden barrels, usually near a river or water source. Serveral  baskets of leaves are put in the barrel, wedged down by various basketry devices and then covered with water. The barrels are left to stand and the fermentation process begins. This job, usually performed by women, can take between three days and several weeks, depending on the temperature. When the fermentation process is judged complete, the leaves are removed, lime is added and the contents of the barrel are beaten to introduce oxygen so that it froths. The mixture is left to stand for a time; a crusty blue froth is usually a good indicator that this step is over. The water is then drained off with scoops, often made from gourds. The indigo paste left at the bottom is poured off into baskets. Many groups among the Miao, Dong, Bouyei and Shui keep a wooden vat in their household to dye their woven pieces.  The vat is kept going all year and is fed with the dye paste that is stored in baskets.

In some villages women send their cloth to be dyed by a specialist. One Bouyei village near Zhenfeng, southwest Guizhou, does not grow indigo to make paste, but buys it on market days from an area nearby. The master dyer of this village, a man, explained that he had kept his dye vat going for ten years, feeding it every night with different quantities of paste and line, according to the desired colour of the fabric he was dyeing, and a very small proportion of industrial soda. The following day he would  produce the right shade of blue. If the feel is not quite right he adds a little rice wine. Several dippings of the cloth give rise to darker shades of blue. In Dong villages it is the women who make the paste and do the dyeing.