Woad plants have been used to make indigo blue dye for thousands of years. I have read that woad seeds have been found stored in Neolithic sites. The use of woad as war paint in Ancient Britain is commonly reported as a fact, so it was disappointing to find that this belief hinges chiefly on Julius Caesar's comment in 'The Conquest of Gaul' being overenthusiastically interpreted. He wrote Omnes vero se Britanni vitro inficiunt, quod caeruleum efficit colorem. This translates as 'Truly, all the Britons stain themselves vitro, which produces a deep blue colour.' It is a leap in the dark to say vitro meant woad, it is more likely to relate to vitreus - glass with a bluish colour. Kym Lambert writes that trying woad pigment in tattoos has a nasty caustic effect without a blue result and it is not great as a body paint either. http://www.dunsgathan.net/essays/woad.htm
Never mind, I shall give up the face paint and go back to expressing war-like intent with a hard stare or sharply worded memo. Before I troubled to read up on the subject, my eye and imagination were caught by a small woad plant in a nursery. I bought it, put it in a sunny spot and it grew huge, with a great cloud of yellow flowers. I read about how to extract dye on this excellent site http://www.woad.org.uk and thought I might just about get the necessary carrier bag full of leaves. Then the plant died.
I saved the seeds and sowed them in a tray, growing little plants which spent the winter in my veg patch, looking very battered. They flourished the following summer and I had a chance to try woad extraction and dying. Got it right the third time, after an unfortunate attempt to make a Sig vat in a chamber pot.
I let one plant flower, but pinched the spike out of the others to keep them growing more leaves. Some seeds I planted last summer and put out in the veg patch, others got the luxury of my unheated greenhouse and are looking pretty leafy already. These are really second year plants and I now know that spring sowing for harvest of the leaves in the first summer is the recommended option. Today being a leaf day on the Biodynamic Calendar, I have sown some of last year's seeds.
Having a load of seeds leftover from the first plant, I soaked them and simmered them and tried dying a skein of double knitting 100% wool in the resulting bath.
The colour of the wool was a slightly greenish beige. Not thrilling, so I added a splash from my jar of clear vinegar with pennies in it, which both acidifies the bath and adds copper, and suspended the skein so half would have the dye colour modified.
The final result is not to die for, fnah fnah. I will wait now for the summer leaves and real blue heaven.