Old World source of indigo dye. Indigo replaced Woad as the main blue dye in Europe in the 1700's, and was a cash crop in the Southern U. S. during the same period. Similar in use and appearance to I. suffruticosa, the leaves are larger, and the seed pods are straight instead of curved. Emetic, antiseptic and astringent. Because it is nitrogen-fixing it is commonly planted as a green manure crop in the tropics, especially in tea, coffee and rubber tree plantations.