In one of the fibers classes I took last year at Arizona State, the professor had us try wrapping gathered leaves and flowers into bundles and simmering them overnight in a light dye bath - I think it was onion skins. This cotton piece turned out the best of my experiments. It was lots of fun (opening the bundles the next day is a little like Christmas!) and I've been meaning to do a lot more of it .... but you know how that goes! So now here I am, surrounded by tons of plants - I'm still trying to figure out what they all are. I'm starting to gather some interesting leaves, etc. to try out.
This technique is actually India Flint's - an Australian textile artist who works with natural dyes and dyeing methods. Her website is a gold mine of inspiration and she also has a blog, Prophet-Of-Bloom, that is lots of fun to follow. Basically, you lay a piece of fabric (silk, linen, wool, cotton, hemp, ...) out flat, lay plant parts on it, and roll or fold it up tightly, binding it with yarn or string. The bundle is simmered in a dye pot for differing amounts of time.
India travels extensively, gathering materials and giving workshops - taking one is on my wish list for someday and if it's on yours you can check out her schedule for the rest of 2013 and for 2014 here.
I'll let you know how my experiments go!
Happy Creating! Deborah