There are a lot of stinging nettles (Urtica dioica)in the UK, growing in the hedgerows, in abandoned corners and down lane-ways.
They are fabulous things to use, while you want to avoid touching them they make great tea (good for hayfever and colds), as a herbal remedy they are used for ailments such as eczema, allergies, arthritis and gout, you can make fabric from them, they make yummy soup ( I have tried them as soup while camping, which made me feel proper wilderness savvy). Recently, I was given as a birthday present a bottle of nettle wine, which was delicious - light, fresh and full of subtle flavours. I plan to brew some nettle beer in the near future (well - realistically in spring)
But to the point - you can use them as dye! I had some plain homespun wool, about 400 grams of it, and I picked about 800 grams of nettles, boiled them up with vinegar and left the wool in to soak for 24 hours. Result? a very subtle, pale warm beige - apparently you get this yellowy beige if you use nettles in autumn, while in spring, while the plants are full of chlorophyll, you get a pale olivy green. I was pleased - unfortunately the wool is a little itchy to use as clothing, but I plan to incorporate it into a fabulous and weird knitted rug... will be posting about that in a little while...
Finally- while coming home from work one evening, I turned into the park, and it was awash with glorious autumnal light filtering through the trees, photos don't really do it justice: