Traditional Dyeing and Weaving: Just What is Indigo?
Just what is indigo? Most of us start out thinking we know, but do we?
The term indigo is, of course, used as the name of a color. To me it is
a deep navy blue with an ever-so-slightly greenish cast. But this is the description of the color called ai () in Japanese. When indigo appears as one of the seven colors of the rainbow in the West it exhibits a slightly reddish cast.
Marsdenia tinctoria – covering Southeast Asia
Marsdenia tinctoria is commonly found in subtropical regions including Nepal, Thailand, Burma, and Indonesia. It is a winding shrub or vine that can grow up to fifteen feet long. It is related to a plant called dogbane.
Indigofera tinctoria – “true” indigo from India
Next, most of us would list it as a plant. But, which plant? Perhaps Indigofera tinctoria, commonly called true indigo? This is the one associated with the blues of India. It grows as a shrub and is in the legume family of plants along with beans and wisteria. It likes a tropical climate. The basic material we extract from the leaves to create blue is called indican.
 Persicaria tinctoriatadeai, or Japanese (buckwheat) indigo
And in Japan there is tadeai (蓼藍), (Persicaria tinctoria), also known as Polygonum tinctorium, or Japanese indigo. It is an annual that grows up to about three feet in height and grows well in temperate climates. It is classed with buckwheat.
Indigofera suffruticosa from the Americas
But indican is found in many other plants and in many other parts of the world, such as Indigofera suffruticosa. Even though it is commonly called Guatemalan indigo, this plant is native to most of the tropical and subtropical areas of the Americas including the Southern United States and all the way down to the northern reaches of Argentina.
indigofera_bracteolataWest Africa.jpg
Mercurialis leiocarpa – Japanese yama-ai
But even in Japan there are more plants than just tadeai that contain indican. There is yama-ai (山藍), Mercurialis leiocarpa, a slender perennial that hugs the ground.  Ryuukyuu-ai (琉球藍), Strobilanthes cusia, has leaves as large as a person’s hand. It is in the acanthus family and has been a long-time favorite source of blue for collectors of Okinawan textiles.
Indigofera bracteolata – West Africa
Indigofera bracteolata grows well in the moist savannah lands of West Africa and thrives in sandy soil.
Strobilanthes cusia – Ryuukyuu-ai, Okinawan indigo
And of course, there is synthetic indigo. It made its first real commercial appearance at the tail end of the 19th century (1897) and quickly replaced the more laboriously produced natural sources. The actual core colorant of all of these sources, including the synthetic, are chemically identical. Slight visual variations can be appreciated among the numerous natural sources brought about by differing impurities in the plants or unique extraction techniques.
Isatis tinctoria – woad, covering Europe and the Middle East
If you are interested in browsing a beautiful collection of photos of Indigofera, visit JuiceyImages, or search for images on the Chinese Herbarium.
copyright John Marshall, 2015
copyright John Marshall, 2015
View of John’s studio from the backyard - the indigo patch is in the lower right corner.
copyright John Marshall, 2015
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