I found a new book!
The Complete Guide to Natural Dyeing: Techniques and Recipes for Dyeing Fabrics, Yarns, and Fibers at Home. By Eva Lambert and Tracey Kendall.
I looked through it at the yarn/textiles store here in Seattle's U District, and highly recommend it.
This book has great photos highlighting the amazing colors obtained from plants.
They also give many examples of overdyeing a previously dyed yarn (such as: yellow from any yellow producing plant/mushroom later dyed with indigo to give a beautiful teal) and of using more than one mordant to give variation in tones (such as copper mordanted yarn in a Sambucus/elderberry leaf dyebath, dying for a while to get a yellow, then adding an iron mordant to add nice brown tones to the yellow).
This book also got me thinking positively about collecting plants for dye starting now or soon. I've heard and read about several dye plants, but need to actually go out and get them. Easy once you find a patch, but hunting for a good patch seems hard.
But SPRING is on the way :)
Some plants on my list are:
Weld (Reseda luteola)
Woad (Isatis tinctoria)
Elderberry leaves (Sambucus sp.)
Pterocarpus santalinus (tree from India, need to order)
Madder (Rubia tinctorum)
Logwood (Haematoxylum campechianum)makes black, purple, grey
I spend my time reading things like this and this and this and this on the internet :)