Indigofera tinctoria (True indigo) is a large shrub, growing 5-10 ft tall and is native to SE Asia. The refreshingly bright, pea-like flowers bloom heavily in June and July, and can sometimes continue intermittently all the way to September. It is grown in USDA Zone 5-11, and prefers full sun and regular water. Apart from its use in making indigo dyes, this shrub has a long ethnomedical history. It is a great garden plant that attracts bees, butterflies, and hummingbirds.
When mature, the plant is hardy to temperatures as low as 30 degrees F for a short period of time. Planting in pots and keeping them indoors during cold weather is also an option for gardeners living in regions with cold weather. To ensure healthy growth, Indigofera tinctoria needs a long growing season. As the flowers bloom on new growth, it is important to prune the plant in late winter or early spring to promote fresh and abundant blooming. With the correct care, this plant will reward you with beautiful blooms and a pleasant, vibrant atmosphere in the garden.
Even more, you can make Indigo dye that has been used for a long time. The leaves of the plant contain a substance called indican, which must be treated with a special process to make the dye. To make the dye, you put the fresh leaves of the plant in water for at least 12 hours, stirring it often. When you are done, you will have a blue substance which is the dye.