2. A plant by many other names can be as blue.
Indigo is not the only plant to produce blue. In Europe and especially Britain it was woad, Isatis tinctoria, a yellow-flowered member of the brassica family, from which the colour was extracted. Woad contains the same chemical as indigo. Indigo can also be extracted from Strobilanthes cusia (also known as Chinese rain bells or temple bells) from Japan and Taiwan, and Indigo suffruticosa from South and Central America. In North America, the Indians used Baptista australis, wild or false indigo, to make blue dye. Rubia tinctorium, the Asian plant root usually used to make red, was also used to make blue.