|Extract of Indigo plant applied to paper (Photo credit: Wikipedia)|
|Baptisia tinctoria 001 (Photo credit: Wikipedia)|
Indigo dye has been prized by humans for thousands of years. During colonial times in America, small cubes of indigo could be used in place of currency.
There are a few plants referred to as indigo. Knowing the differences between these plants will help you to provide for their very different growing requirements.
Baptisia tinctoria is the false or wild indigo that grows throughout North America. While the rhizome can be soaked in water to produce a blue dye, it is not the famous indigo dye plant - the so-called true indigo (Indigofera tinctoria).
In most parts of North America, false indigo can be found in the wild or in flower gardens. Baptisia thrives in most temperatures (as far north as zone 3) and a wide variety of soil types. The flowers may be yellow, blue, pink or white, but the prepared rhizomes all produce a blue dye.
If you're interested in growing the true indigo, you'd do best to invest in a greenhouse as this plant is native to India and needs positively steamy temperatures to survive. It may grow well in Florida, but won't do well in the rest of the country unless grown under glass either in the home or the greenhouse.
Two alternatives for those interested in growing their own blue dye plant are European Woad (Isatis tinctoria) and Japanese indigo (Polygonum tinctorium), both of which also produce blue dye.
These plants are a happy medium between the super-fussy true indigo and the super-easy false indigo. They need warm temperatures, but it doesn't need to be steamy and the plants can be grown outdoors in much of Norther America, as long as you provide them with plenty of sun, water and fertilizer.
Dye from the Japanese indigo is produced from the leaves, rather than the rhizome, which makes for easier harvesting that can be extended over several weeks if desired.
Have you ever tried growing any of the plants called indigo?