natural dyeing - plants that make blue dye

Let's complete a list of plants that we can use to dye, wool, cloth, cotton, linen, and other textiles, the colour blue.  

No need to restrict to region or climate, we're looking for a master list of natural dyes.

So far, I've played with

woad


and

indigo


both of them use fermentation to make a brilliant blue colour.  

what other natural dyes can be used to make the colour blue?

I've been reading online about black beans as a source of blue dye - and I'm willing to give it a go, but has anyone tried it and then done a light fastness test?   It's most frustrating if the colour fails to stick.

I have tried black bean and the color is from anthocyanin in the skin. So it is pH sensitive and the  reactions to fibers are totally different from those traditional indigo based pigments.
I would soak the dry beans in cold water just long enough to loosen the skin from the beans and rub off the skins for further extraction. If I leave the whole beans soaking for too long, there will be substances leaching from the beans and microbes will begin to grow and turn the water acidic. It's time consuming to get lots of pigments from black beans this way.

I do not have experience creating a dye from it, but could red cabbage potentially be of use? I believe with some PH play you can get a blue color from it.

I don't know if they are appropriate for dyeing, but blue as a color in nature has long fascinated me, and so here are two tidbits....1. yarrow essential oil is intense blue (as well as a certain kind of chamomile, and possibly other plantss)  I don't know if one can dye with oil, and it would be a pretty profligate thing since it takes a huge amount of plant material to produce a small quantity of oil.  2. blue ash (Fraxinus quadrangulata), a rather uncommon Midwestern ash (which also has the property of moderate resistance to emerald ash borer), apparently will stain water blue if you stir green twigs in it.  

Copper mordant is blue green, and will dye cloth that color. Of course, if you add enough to get a strong aqua/teal, it'll damage the fabric.

cloth dyed with just copper. I think they made this dye with copper pennies

The Aqua is made with copper

I found the copper mordant was strong enough to turn my cochineal dyes to a lovely shade of purple.

 do not have experience creating a dye from it, but could red cabbage potentially be of use? I believe with some PH play you can get a blue color from it.

In the liquid form yes - but for the life of me, I can't get either red or blue to stick - just blah beige.  It's most frustrating.  Guess it goes into the "eat only" basket.

I wonder how light fast cabbage skin dye is? I once dyed Easter Eggs blue with mulberry juice. They were a lovely blue when we first dyed them:

The blue ones were dyed with mulberry

But the sunlight destroyed the blue in the time it took my kids to find them:

Blue egg in the front was in the sunlight and has a large, bleached spot from the sun

I stumbled across this just now, from Rosalie's Medieval Woman [url=https://rosaliegilbert.com/dyesandcolours.html]Medieval Dyestuffs, Dyeing & Colour Names
DYESTUFFS - MORDANTS & FIXATIVE - NOTES ABOUT COLOURS - MEDIEVAL COLOUR NAMES[/url]:

- Whoever wishes to make a fast blue, take ground lapis lazuli pigment in lime water and boil it with gum arabic and with alum and dye therewith. If he wishes to make it dark, add black dye thereto and blue flowers which stand in the field, and mash it well and boil it in urine and mix it with alum and dye therewith.
- Take the leaves of a dwarf elder and mash them and take indigo and add thereto and grind it together and let them dry together for a long time and take lime water and let it seethe together and then take alum and grind it thereto while it's all hot. Paint it on white fabric, and it will become a good blue.

Solving the 1000 year mystery of rare blue medieval paint

The color is called folium, and it was used as early as a thousand years ago. It fell out of favor by the 19th century, and scientists tried recreating it and discovered its source in the century that followed.

...

They looked to medieval sources that credited the plant, Chrozophora tinctoria, as a natural source of color that created blue and purple dyes. They were stored on cloth and dried as watercolors. When it was time to use them as paint, a piece of cloth was cut and the paint was extracted with water or another element to bind it to the page.

Books from the 12th, 14th and 15th centuries described the plant, when it should be collected and the delicate way to process it.

The plant is a small, unassuming herb found in the Mediterranean, North Africa and central and southwestern Asia, according to the study. It’s usually spotted in dry areas and along the edges of agricultural fields.

...The medieval recipes told them in detail not to break the fruit open and release the seeds. They were able to extract the compound responsible for the blue pigment from the fruits, isolate and purify it to successfully reproduce the color.

From Science Direct Scientists Discover a New Compound in Medieval Ink That Was Once Lost to Time

The molecular structure the team found was dissimilar from other blue pigments extracted from plants, such as indigo and anthocyanins, the blue pigment found in berries. But it did have a structure in common with a blue chromophore found in another plant - the medicinal herb Mercurialis perennis, or dog's mercury.

With a key difference: the chromophore in C. tinctoria has a stable glycosylated structure, which means it is water soluble - and can therefore be transformed into a dye.

This discovery means that not only can conservators and scientists recreate the dye to probe its properties, such as its structure and how it reacts to environmental stresses over time, but they can better identify it in medieval manuscripts.

"Chrozophoridin was used in ancient times to make a beautiful blue dye for painting, and it is neither an anthocyanin - found in many blue flowers and fruits - nor indigo, the most stable natural blue dye. It turns out to be in a class of its own," the researchers wrote in their paper.