How to Dye with Indigo: Natural Homegrown Color

image of 3 photos showing a japanese indigo leaf and fabric dyed bluish green with indigo

Indigo has been used to dye textiles for thousands of years, traditionally using a fermented dye vat. Freshly harvested Japanese indigo, sometimes known as Dyer’s Knotweed, produces a luminous mermaid blue to seafoam green color with minimal processing. In this tutorial, you’ll learn how to dye silk with fresh indigo leaves.

The plant, whose botanical name is Persicaria tinctoria, is an annual that’s easy to grow from seed in the summer garden. One-part natural wonder, one-part botanical alchemy, extracting color from homegrown Japanese indigo is a marvelous garden craft project you can make with common kitchen supplies.  

You’ll get the most vibrant blues on protein or animal fibers, like silk or wool, although cotton, linen and other plant-based fibers will produce lovely greens, like teal, celadon, and jade. 

image of various textiles dyed teal blue with fresh indigo leaves: yarn, strips of fabric

What You’ll Need

  • Fresh Japanese indigo leaves. To extract color, you’ll need to use freshly harvested Japanese indigo leaves. You’ll need to grow your own plants or partner with a friend who has a garden. If you’ve ever grown a sunflower or zinnia, you can grow Japanese indigo. No garden? Even a container on a sunny patio or balcony can produce a small crop of lush foliage. 
  • Metal or glass bowl 
  • Silk ribbon or yardage, pretreat by soaking in cool water for several hours or overnight to thoroughly wet the fibers. 
  • Ice water
  • Salt 
  • Dishwashing gloves 

How to Dye Silk with Japanese Indigo

  1. Harvest stems of Japanese indigo. To test if your plants are ripe for dyeing, pick a leaf before harvest day. Allow it to dry for a day or so. If the leaf dries to a dark blue, you’re good to go. To encourage subsequent harvests, leave a few inches of growth remaining at the base of each plant. They will continue to produce new growth until frost or cold weather puts an end to the growing season. image of fresh green Japanese indigo leaves on the left and a single dried, blue-ish leaf on the right
  2. Strip leaves from your harvested stems, adding them to a bowl filled with ice water as you work. It is important to keep the leaves cool. This delays a natural chemical process within the plant cells that combine to create the indigo pigment. Once you’ve removed all the leaves and are ready for the next step, drain ice water. closeup image of fresh green leaves floating in ice water
  3. Sprinkle 1 to 2 tsp of salt over your bowl of leaves and begin to gently massage. Pretty quickly you’ll see how the salt draws water out of the plant. Keep massaging the leaves until a puddle of green liquid forms in the bottom of the bowl. Pro tip: Japanese indigo is non-toxic, but gloves will keep your hands from turning blue. A layer of newspaper will protect your work surface. image of green leaves in a bowl with salt on them and a rubber-gloved hand rubbing salt into the leaves
  4. Add your dampened silk/fiber to the soupy plant mixture. Continue working the liquid and the broken down Japanese indigo leaves into the fiber. At first the silk will take on a greenish hue. But as you continue to massage the mixture, the color will start shifting toward turquoise blue as the indigo oxidizes. Periodically lift your material out of the dye bath to check the developing color and further expose the fiber to oxygen. image of 2-part process: on the left, yellow-green silk fabric dyed in a metal bowl with wet leaves, and on the right, the same fabric and leaves oxidized so the fabric is now blueish green
  5. After about 10 to 15 minutes, remove your fiber and hang it to dry. Remember to protect any surface that dripping dye might stain. Don’t worry about removing little flecks of plant matter, it’s easier to flick them off once the material dries. Wait a day or so before rinsing your fabric in cool water to allow the dye to fix to the fiber. image of blueish green naturally-dyed fabric strips hanging to dry on leafy branches outside

Lorene Edwards Forkner is a gardener, designer, author and educator. She lives a garden-based life in the Pacific Northwest, specifically in an old house near the beach in West Seattle. Her newest book, Color In and Out of the Garden, guides the reader through observing and recording nature through a watercolor painting practice. Paint along with Lorene in her class of the same name: Color In and Out of the Garden.