Japanese indigo (Persicaria tinctoria) in the garden and the dye pot


This month, I made my first indigo vat, guided by an excellent article by Isabella Whitworth and Christina Chisholm, published in the winter 2011 issue of the U.K. Journal for Weavers, Spinners and Dyers. The article is available online as a free download from the journal:


In a recent blog post, Isabella (dye expert, textile artist, teacher, independent scholar and dye editor for the above journal) adds some very useful notes to the dye experiences reported in her 2011 article. Check these out on her blog at http://www.isabellawhitworth.com; see also some other suggestions for dye authors on my reference page here. The link to Isabella's article is also in her most recent post about Japanese indigo

All the instructions needed for your Japanese indigo vat are there. Please disregard the journal links I sent in the original version of this post (if you saved it) and see my “Stern Footnote To Self” at the end of this post.

Japanese indigo is not a native of North America or Europe and has a bit of a rep for being frost-tender. Despite my limited experience of it, I have found it a plant with a violent will to live and leave a legacy. It sets seed abundantly, though seed viability is limited, maybe not more than two years from harvest.

In the photo below, you see that at every node, the plant grows long roots. These two-and-a-half-foot-long stalks of indigo were in a bucket of water for three days after I had cut the plants for the dye pot, and then got too busy to make the dye. The indigo rooted overnight at each node under water and bloomed after a day.


I obtained the seeds some two years ago from another textile artist and dyer in Ottawa, Debra Percival; Debra is also an accomplished printmaker and devotee of non-toxic printmaking. Debra starts her seeds indoors, then pots the young plants up in planters on her small patio. She notes that after composting unused plants that have set seed by the fall, she often finds plantlets growing in the compost in late spring from overwintering seeds. Find Debra at http://www.landfillart.org/debrapercival

I planted my first batch of seed in a pot outside in May two years ago…and forgot all about it that year. We had begun the process of selling our former house and indigo vats were struck off the agenda….Come October, I found the pot, plants still cheerful, and brought it inside to more neglect on a cold floor near a window. Though the plants looked scraggy and tatty, some pink flowers boldly showed up and set seed by Christmas…and by late February, seedlings appeared, became plants and yet again went to seed in the pot – only to suffer neglect for another year! It was the seeds from this second batch that provided the plants for the vat of 2014. Here they are, blooming and setting seed even in a pot of water:


Most dye authors (but not all) that I consulted ( see my Reference page) advised cutting the stalks before the plants bloomed, since dye could not reliably be extracted if the plants were in flower. The time to harvest leaves for the vat? Just before the bloom time! But I saved a few long stalks from the scissors to keep for seeds next year. Perhaps unnecessarily: the plants I cut at two nodes above the soil are now over twelve, lush, leafy inches high and it is barely three weeks since I collected the first harvest. Mind you, the fish fertiliser we use helps plants produce more leaves…


But after cutting down all the plants quickly before they could bloom, I found myself with too much indigo to deal with in one session. All the leaves from one planter full of plants were therefore dried and stored for “later”, while the harvest from the second planter went into the pot. And Lord knows what amount will yet arrive from the the plants that are now regrowing…I think I may get two more harvests.

Here is the first batch of dried Japanese indigo stalks and leaves; not sure if the stalks give colour, though…

Leaves stripped from the stalks and laid out, fresh and green:


After a day drying in the hot sun, the blue pigment begins to appear. I stored the dried leaves in a tin.


The dried stalks become bundles of warp on the garden loom:

And now the vat.

For my first indigo dye experiment, I used a (well-scoured) yard or so of silk velvet that had been an eco print flop last year.

I used a thrift shop electric turkey roaster with a thermometer gauge that allowed me to set and hold the temperature of the water in the pot to well below a simmer. I filled the pot with leaves, covered them with ice cold water and left them to warm for several hours, until the temperature reached 160F/60C. ( Slow warming ensures that the blue pigment is not destroyed.) The pot of leaves by then had changed colour to look like sherry:


After straining out the leaves, I added washing soda (sodium carbonate/soda ash) to the liquid, one tablespoon (15ml) at a time, until the liquid turned a kind of slimey green. Then I beat the water like mad with a whisk until It got frothy:


When I had plenty of froth (more than in the pic above), I heated the liquid in the vat back up to 160 C, then dissolved a tablesoon (15 ml) of thiourea dioxide in the liquid in order to remove the oxygen from the vat. I think I added a bit more than that, for good measure. This turned the liquid greeny-yellow. After a few minutes, I entered some silk velvet into the pot and left it submerged for about three minutes.

In the picture, you can see the silk beginning to turn aqua blue as areas of the fibre become exposed to the oxygen in the air.


Exposed to the air, the yellow turned aqua-green-blue.

Voila! I obtained this shade of green-blue by dipping the silk textile three times in the vat, each time for about three minutes, and hanging it for about five minutes each time. The textile had been eco printed once before but not very successfully, hence the yellowy-brown blotches on the surface.


The next step was to see if the indigo textile would accept fresh eco prints from plants with the pigment concentration that is available at this stage in the season. I layered the silk with aronia berries, Japanese maple, Cotinus obovatus and a few tansy buttons:


And finally, a Stern Foot(In Mouth)note to Self:

The only things in life that one can say one truly owns are one's mistakes.

Dear readers, please note the mea culpa: This blog post is an update of the one from the early hours of Labour Day in Canada in which I made three bad editing blunders with reference to the Journal for Weavers, Spinners and Dyers.

I offer my apologies to Isabella and the Journal. Please destroy my most recent post about indigo if you saved it and note the following:

1. I gave the link to Isabella's article about dyeing with indigo (see first para, above) without checking that the site listing “free” pdf's had, in fact, received permission to reprint the article from the Journal for Weavers, Spinners and Dyers. I did not check (ouch) to see whether this site had permission to offer the JWSD article for download. I will not give the name of the site because they do not deserve any more publicity. I am truly repentant for my carelessness here.

2. Isabella's link is as follows: http://www.isabellawhitworth.com

3. Isabella is still the dye editor of the journal, not recently retired, as I, in my fog of indiscreet errors, stated.

And as one last note: I had also linked Isabella's name to the Midsomer Murders series…thank God it is no longer midsummer….




16 thoughts on “Japanese indigo (Persicaria tinctoria) in the garden and the dye pot

  1. Hi Wendy: Many thanks for putting the links right so swiftly and also drawing the Journal for Weavers, Spinners and Dyers’ attention to the ‘naughty’ download site.
    I’ve been really interested to read your experiences with Japanese indigo and as always, your images and commentary are informative, useful and very interesting.
    I hope you have managed to remove your foot from your mouth now; at my age such a concept is somewhat academic.
    And how about a new series called Midwinter Murders…??

    1. Gracious as always, Isabella! Thank you. I have learned, yet again, that one cannot be too careful with communications via the internet. Since I am pretty touchy myself about people not crediting work properly, mine included, I am making myself even more aware of the need to practice what I preach.

  2. hi wendy, I am glad to see your indigo post. I have some growing in the garden and they are rather finicky as they like too much water. A friend who is moving away, gave me a pot of her organic dye vat and I’ve using it for some of my experiments. When this pot has exhausted, I’ll try making one using your tips. Thanks for sharing

    1. Hi Melinda,

      Indeed, these plants love water! And sun. But I am happy, now that I am in the third summer of Japanese indigo, to finally give it a try. I am looking forward to seeing whether or not the dried leaves will give good colour. Plus at other ways to get the vat to produce the blue pigment beaides with the thiourea dioxide

  3. Hi !

    I really enjoyed reading your article on persicaria tinctoria.
    I plan to soon run a small farm growing dye and fibres plants. This is the website of the project, for now. It’s only a beginning and the site is only in french for now.
    This summer, I want to grow dye plants and I really need to find Japanese indigo seeds as it is the one I cherish the most. I’m really looking forward to finding seeds that comes from plants grown in Canada since I live in there and that they would be probably more adapted to the climat. I was wondering if you had any extras seeds that I could buy to you or maybe help me find someone willing to send me some !

    Thank you, and have a nice day !


    1. In case you did not receive my email on your site: yes, I have seeds but at your own risk! they sometimes fail to germinate.
      Phone me in Ottawa if you’d like more info, and just send me an email with your info. In return: no charge, just share the seeds of your harvest. That is how I obtained mine.



  4. thank you so much! i would love to know how to use the seeds from my present crop? do i extract them from the flower bloom and if so, when? how? or, what method should I use?

    1. Hello Ms Doe!
      Cut the seed heads off when the flowers turn pink. Dry them by hanging upside down inside a paper bag. Sow the seeds indoors six weeks or more before your last frost date. Plant out in pots or a sunny spot. They like lots of water. The seeds are usually viable only for one year after harvest. Good luck! I planted my own seeds too late last year and the plants failed to set seed before frost, so plant early!

      1. Thanks so much I’m a little confused about the cutting of the seed flower. I don’t see a seed yet should I cut them now? Place upside down in paper bag and then sow them when it’s warm again? Keep them in the paper bag how long? I’m new sorry so many questions lol

        “And those who were seen dancing were thought to be insane by those who could not hear the music.” Friedrich Nietzsche

        Deborah Charles Founder/CEO Two II Films LLC https://twoiifilms.com

        Sent from my iPhone


      2. Google “persicaria tinctoria seeds” to get a photo. When you see your plants have. the same tiny tiny pink flowers, check them by shaking the flower head inside a paper bag. When the seeds start dropping out, time to harvest. Dry the flower heads as I described. The seeds will drop off with good shakes of the bag. Others maybe have different methods so do some searching if mine does not work for you. The important thing is to gather them before the frost. They self seed and grow readily – you may even see baby plants growing around the parent plant once the plant has set seed. This is a plant with a will to live.

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