"Who, we might wonder, was able to guess that concealed within the fibres of certain green leaves lay the deepest and most mysterious blues?" writes Catherine Legrand at the beginning of Indigo: The Color That Changed the World ($50, Thames & Hudson).
She's referring to polygonum tinctorium, or dyer's knotweed, a viridescent plant that, after a year-long fermentation, creates a blue so true it anesthetizes all those who gaze upon it.
More important, it can be used to craft a supreme pair of jeans among a sea of synthetically dyed, mass-produced posers. Tokushima, a prefecture of the Japanese island of Shikoku, is one of the largest producers of this dye, used in the Japanese denim sought after by luxury brands like Tom Ford, Louis Vuitton, and Prada.
If you're in the region, visit The House of Indigo (Aizumi-cho, Tokumei Aza Maesunishi), where, for a small fee, you can plunge handkerchiefs into smelly blue vats using the shibori (tie-dying) method. It's good fun, but be sure not to get any on your hands--the stains could last longer than even the most premium denim.