The subject of natural dyes featured in a recent post [26/08/19]. Susan and Ashley who have the neighbouring allotment are expert dyers and their website/blog Nature's Rainbow is a mine of information. As I mentioned several of us gathered at their house to do some dyeing; in particular we made Indigo from the leaves of Woad (Isatis tinctoria).

 Which reminds me that several years ago I helped some permaculturalists plant a garden of dye plants at Morley College in London which has a highly regarded textiles department. Zoe Burt who teaches there gave a demonstration of dyeing using Weld (Reseda luteola) and we each dyed a silk handkerchief in a luminous shade of yellow.
 I read somewhere that if Weld is overdyed with Woad it creates Lincoln Green; I'll have to give that a go sometime. 

 We generated other colours with Susan and Ashley that day using the flowers of Dahlia, Rudbeckia and also crushed Cochineal. These resulted in various vibrant shades on the yellow/red/orange spectrum.
 Plants as a topic generate so many avenues of inquiry: food, medicine, dyes et al. I don't have the time to explore every aspect in the detail it merits but it's fascinating to gain these insights from people who have specialised knowledge.