Monthly Archives: June 2019

Shows Devil's Bit Scabious plant in early June with lush green leaves but not yet in flower. Inset is blue composite flower from previous year

Devil’s Bit Scabious as a source of indigo?

By Ashley Walker
Copyright 15th June 2019

Scan of page 62 of Traditional Scottish Dyes by Jean Fraser showing entry on Devil's Bit Scabious

Scan of page 62 of Traditional Scottish Dyes by Jean Fraser showing entry on Devil’s Bit Scabious.

Front cover illustration showing plant dyed yarns

Scan of original reference from Chemical Dictionary of Economic Plants aparently confirming that a blue dye can be obtained from this plant

Reference to Devil’s Bit Scabious from Chemical Dictionary of Economic Plants

Some years ago I came upon a reference to this bee-friendly and pretty blue flower being a potential source of blue dye in Jean Fraser’s book “Traditional Scottish Dyes and how to make them”. Jean attributed her information source to Ethel Mairet. In her 1916 “Book on Vegetable dyes” Ethel briefly mentioned that Devil’s Bit Scabious leaves, if treated like Woad, will give a blue colour but adds no further details. A quick internet search brought up a number of other references to this plant producing either a blue or green dye. Significantly an entry in “Chemical Dictionary of Economic Plants” (2001) edited by Jeffrey B. Harborne, and Herbert Baxter, states that fibres placed in an alkaline fermentation bath of the leaves will turn blue on exposure with the air, though the active chemical is not identified as indigo. Devil’s Bit Scabious (Succisa pratensis) a member of the honeysuckle family (Caprifoliaceae) and a related plant is Teasel (Dipsacus), which in turn is also mentioned as a source of blue dye – being apparently produced by dried flower heads.

At the time I was looking out for possible dye plants that had flowers that weren’t yellow, as this would make our dye garden a little more attractive to the eye. I am also a beekeeper and Devil’s Bit Scabious was being promoted as one of the most pollinator-friendly native flowers, so I set about obtaining some seed. I was disappointed however to find that although you can buy the seed it has very poor viability. My first attempt resulted in no germinations and the second attempt only produced 5 plants out of around 500 seeds. In the end I bought some plants from the Rosy Bee plant nursery and planted them in the dye garden where they have positively thrived. Finally (3 years later) I had enough plant material to try extracting the blue dye.

Method

Leaves of the Devil's Bit Scabious looking very much like Woad leaves

Basal leaves of Devil’s Bit Scabious which bear close resemblance in both size, colour and shape to Woad leaves.

All references to the extraction process say that the basal leaves should be used and that they should be treated just like Woad i.e. placed in an alkaline fermentation bath (possibly the urine bath). I was not happy about using urine, so instead opted for Jenny Dean’s recipe for hot extraction of indigo from Woad using ammonia as the alkali. In addition, I did a more conventional dye extraction by simmering the leaves for 1 hour and straining the liquor; then dyeing mordanted wool yarn in a heated dyebath with and without adding soda ash to raise the pH. Finally I set up a solar dyeing jar with leaves, wool yarn and some soda ash to make the liquid alkaline and set it aside in a warm place to ferment.

Results

Jenny Dean’s indigo from Woad extraction

After pouring boiling water over the leaves and leaving for an hour and straining, I obtained a pale yellow liquid.

Shows pale yellow colour of Devil's Bit Scabious liquid extract

Pale yellow liquid extract.

showing green liquid produced by adding ammonia

Adding the ammonia turned liquid a dark green.

 

 

 

 

 

 

shows colour change from dark green to orangy yellow after reducing agent added

Colour change after adding Thiourea Dioxide to the green liquid.

There was no sign of any free indigo nor the characteristic sherry colour from Woad. The next stage, adding the alkali and aerating was exciting because the liquid quickly went a lovely dark green, exactly as one might expect if there was indigo in there. I had my hopes up now for the first time! The next stage was to add a reducing agent and for speed I used a tiny amount of Thiox (Thiourea Dioxide). The colour of the liquid immediately changed to an orangey yellow – too fast for the normal indigo process.

Both samples of yarn shown are the same shade of white

Unmordanted raw wool yarn vs unmordanted dipped yarn. Left: raw wool; Right: dipped wool.

But I put in some un-mordanted wool yarn anyway and waited. I took the yarn out but obtained no discernible change in colour at all. Disappointment! I did several dips and left the yarn in for about 15 minutes, then did more dips, but sadly there was no colour change.

After drying, the wool does look slightly altered but it’s a bit of a stretch of the imagination to see any blue.

Later, I took some of the original green coloured liquid which had the alkali added and neutralized it with some distilled vinegar. The colour instantly changed back to yellow, indicating pretty conclusively that there was no indigo in it.

Color changes from green to orangy yellow when liquid is neutralised with white vinegar

lowering the pH of the green liquid with vinegar brings it back to an orange yellow.

Conventional extraction

Pale yellow alum mordanted wool top. Grey iron mordanted wool bottom

Mordanted wool yarn dyed in liquid extract before alkali was added.

Alum mordanted wool gave a pale straw yellow with no hint of green. Dyeing time ½hour.
Iron mordanted wool, unexpectedly, gave a rather nice slightly warm grey. Dyeing time 15mins.

Shows different colours obtained by mordanting the wool with alum, copper and iron

Colours obtained with three different mordants after leaving in alkaline Devil’s Bit Scabious dye bath over night.

After adding the soda ash, the liquid darkened off as expected to a greeny yellow though not as green as when using ammonia. Wool samples mordanted with alum, iron and copper were introduced and, after rinsing in clean water, produced a similar set of colours after about ½ an hour. At this point I decided to leave the samples in overnight. In the morning the alum mordanted sample was much the same but the iron mordanted sample had turned from grey to a warm brown. The copper mordanted wool was an attractive greenish bronze. Depth of colour had not increased during the night. Rinsing the yarn removed the green tint of the dye bath.

Discussion

The acute sensitivity to pH tells me that the chemicals producing the green colour in the alkali extract are not dyes and will not even attach to mordanted wool. The grey and light brown colours obtained with mordanted wool suggests that there are natural tannins in the leaves and also a yellow dye. The entry in the “Chemical Dictionary of Economic Plants” says the active dye chemical is a seco-iridoid glucoside. Internet searches suggest that these molecules protect the plant from predators and pathogens and are of interest for their anti-oxidant, anti-inflammatory and possible anti-cancer properties. I did find a reference to an iridoid called genipin which in a weak acid is reported to produce a soluble blue pigment in the presence of oxygen with potential as a food colourant. But to obtain this blue pigment seems to require a chemical laboratory! And there appears to be no logical chemical link to the indigo molecule.

I speculate that the mythical blue colour is one of those confusions that get passed from one source to another without anyone really testing it out. If by some miracle there is a blue dye to be had it is not indigo. Possibly someone at some point mistakenly put Woad leaves into a bath of Devil’s Bit Scabious, they are remarkably similar in shape and size. Or perhaps someone just assumed that since the blue/green was obtained in an alkaline bath identical to a Woad leaf extraction bath then they must be the same dyes.

Shows jar filled with leaves of Devil's Bit Scabious, water with a bit of soda ash added and wool yarn.

Hopefully this solar dye jar experiment is about as close as I can get to the original assertion that Devil’s Bit Scabious fermented in an alkaline liquid will give blue.

The results of the solar dye experiment will take some time. I think it is unlikely there will be any blue or green but we will see.

One further thought, there could be a bit of a pattern developing here, searching for a blue from Elecampane root (see blog post) I discovered a rather nice grey could be obtained. Here again I get another grey. Perhaps this is more evidence that the colour grey was often referred to as blue in earlier days.

Well, I’m keeping the Devil’s Bit Scabious in the Dye garden. It really is a fantastic pollinator-friendly plant and it looks good too.

References

Handbook on Natural Pigments in Food and Beverages – Industrial Applications for Improving Food Color. Edited by: Reinhold Carle and Ralf M. Schweiggert. 2016.

Jenny Dean’s Wild Colour. http://www.jennydean.co.uk/

Resources

Rosy Bee – Plants for bees.
http://www.rosybee.com/plants/devils-bit-scabious-succisa-pratensis

Image showing young seedlings of Japanese Indigo in premature flower

Premature Flowering in Japanese Indigo

By Ashley Walker
Copyright 10th June 2019

This year I’ve had two reports of people in the UK growing Japanese Indigo from our seeds and experiencing premature flowering in May. I also read with interest Deb McClintock’s blog post about her early self-seeded Japanese Indigo (in mid-Texas in the USA) which germinated in early February and flowered in May. In the first two cases the plants were not remotely big enough to harvest, so this is very disappointing – doubly so since once the plants put out flower heads the amount of indigo in the leaves starts to decrease. Deb McClintock was able to harvest her “bonus crop” but she noted that it had not grown as well as her normal summer crop. Ideally the plants should grow to a large size before flowering in August/September.

So what is going on and what can be done to prevent this?

In all plants, flowering is often stimulated by the experience of stress e.g. unnaturally high or low temperatures, insufficient water or nutrients and pest damage. However, in the above examples the plants were being treated very well. My first thought was that the main cause of the early flowering was day length. In all three cases the Japanese Indigo seeds germinated in January/February when the day length is short. However, I can’t rule out low temperatures since this is the middle of winter in the UK (latitude=50deg N) and the night-time temperature in Mid Texas is going to get pretty low. Also in the UK in 2019 we experienced a Spring with extreme temperature swings and unusually late frosts.

I can find no definitive information online to suggest that low temperature is a known trigger for flowering in Japanese Indigo. But looking in my copy of ‘Handbook of Natural Colorants’ I see that day length is reported as the critical factor for Japanese Indigo, but other influences are not excluded. However it does say that Chinese Woad (Isatis indigotica) will flower if it experiences night time temperatures below 10°C (50°F).

In all three reports of early flowering, the plants received no artificial lighting and were grown in relatively frost free conditions, although they probably did experience night time temperatures well below 10°C. But of course the day length conditions in mid-Texas are considerably less variable than in the UK. (Mid-Texas latitude is approx. 35 degrees North compared to approx. 50 Degrees North here in Southern England).

The Handbook of Natural Colorants recommends sowing Japanese Indigo in April in mid Europe, with a first harvest in July or early August just before the flower heads start to form. It’s interesting to note that by this point in our summer, the day length has started to shorten but night-time temperatures are usually still over 15°C (60°F), so that should rule out cold temperatures as a trigger and points the finger at shortening day length.

However, my own observations in Hitchin for 2018 is that flowering was very late (September/October) following an exceptionally hot long Summer and warm Autumn. This is a much later flowering than normal.  This is confusing because it suggests that the high temperatures prevent day length from being the dominant factor in triggering flowering. No doubt someone out there (perhaps the professional Japanese Indigo farmers) will know the definitive answer but at the present time I’m not sure if it is short day-length or temperature stress which is the most important trigger for flowering. But in either case the solution is the same.

In Southern England, no matter how warm the early Spring, don’t be tempted to sow your Japanese Indigo seeds before April, unless you are able to give them some artificial light to lengthen their day. Giving them a little warmth (particularly at night) is a good idea too. If the plants do start flowering early, pinching out the whole top of the plant may reset them back to vegetative growth. If the plants are large enough it may also work to take stem cuttings in water (cut out the flowering tips). If these measures fail, new seeds can still be sown as late as June in the South of England.

shows seeds being propagated with extra lighting supplied by a rack of flourescent bulbs. Purpose is to boost light levels to stop seedlings becomming "leggy" and also to increase day length

In my own case, I use heated seed trays and artificial lighting on a timer.

 

Happy growing!

References

Handbook of Natural Colorants (2009), edited by Thomas Bechtold and Rita Mussak, Chapter 7 by Philip John and Luciana Gabriella Angelini.

Deb McClintock’s blog, https://debmcclintock.me/2019/05/27/new-tools-dried-indigo/

Thanks to:

Brian Bond for the photo of Japanese Indigo in premature flower.

Sue Prior