If you can find it, I recommend the Oxford Dictionary of Plant-Lore.
It is a paperback volume with the standard Oxford style cover. My friend picked one up in a remaindered bin for £5. I thought it was excellent so I went online to try and find a copy. Apparently it is now out of print and much sought after:
http://www.abebooks.com/servlet/SearchResu...d&sts=t&y=0&x=0Still, much cheaper in the USA than over here. In England the last copy I saw was going for £260, about $525!!
Another good one is this:
http://www.treadwells-london.com/deCleene.aspAgain, it is expensive, but very cool.