Utah State University Extension is bringing traditional indigo dyeing back into home gardens with a comprehensive three-part guide to growing, extracting, and dyeing with Japanese indigo (Persicaria tinctoria). With a history tracing back to Japan and China, the plant produces the vibrant blue dye that has been used to color textiles for centuries. Whether you’re a home gardener, clothing designer, or fiber artist, USU Extension’s three-part series provides everything needed to cultivate and use Japanese indigo for plant-based dyeing.

Growing Japanese Indigo

Japanese indigo thrives in warm, well-drained soil with full sun exposure. Though not drought-tolerant, it can be successfully grown in temperate climates with proper irrigation. Seeds should be started indoors and transplanted after the last frost, ensuring that plants receive at least 6-8 hours of sunlight daily. With careful maintenance, Japanese indigo can be harvested multiple times during the growing season.

Japanese indigo is a fast-growing, rewarding plant for home dyers. It provides an accessible way to create natural dyes and incorporate gardening into textile arts.

There is a revival of using dyer’s woad to create these blue pigments in Europe, where the plant originated. In Utah and most Western states, dyer’s woad is classified as a noxious weed.

Extracting Indigo Pigment

To transform Japanese indigo leaves into a long-lasting blue pigment, the leaves undergo a fermentation extraction process. After harvesting, the leaves are submerged in water, where they release indigotin, the chemical responsible for indigo’s signature shade of blue. The extraction involves fermenting, aerating, and drying the pigment into a powder which then can be stored for future dyeing projects.

Once extracted, the pigment is ready for use in traditional indigo dye vats, allowing for repeated use in textile projects. The process requires patience, but the result is a rich, natural dye that has been used for centuries in fiber arts.

Dyeing with Japanese Indigo

The USU Extension publications outline two methods for dyeing with Japanese indigo: fresh-leaf dyeing and indigo powder vat dyeing.

Fresh-leaf dyeing involves using recently harvested leaves to achieve green-aqua hues, which work best on protein fibers such as silk and wool. The leaves are either kneaded directly onto the fabric or blended into a dye bath.

Indigo powder vat dyeing follows the traditional indigo dyeing process, using a chemical reduction method to create deep blue shades. The pigment is mixed with ingredients such as fructose and calcium hydroxide to prepare a dye vat that allows fabrics to absorb and develop the indigo color.

Working with natural indigo is both an art and a science. From soil to fabric, the plant connects people with historical dyeing traditions and provides an eco-friendly alternative to synthetic dyes.

Other contributors to the fact sheet series are Elizabeth Cohen, Extension agriculture and small farms assistant professor, and Toree Park, Extension intern.