I'm not quite sure how this works, but I hope I'm in the running for your book, which I didn't know about until this minute. A friend in the UK started talking about sea kale and other perennial veg, and I've read up a bit and not been able to find seeds in this country. Perhaps you can help me? So far we're very into dandelion greens and purslane mixed and cooked, maybe with something from the onion family and bacon fat, and we look forward to branching out.
Thanks for your work!
Its a good time to be an adventurous gardener. The Internet offers access to a lot of seeds and other resources that were very hard to find a few years ago. A few places you might look (there are many others as well) for unusual seed varieties:
Peaceful Valley Farm Supply
http://www.groworganic.com/ very large selection of organic seeds and supplies including good range of cover crop seeds and agricultural tools, geared toward organic farms and larger gardens