ClairBear Robin Goodfellow is quite a fascinating little riddle isn't it! I'd guess you're right about there being somekind of remedy or recipe contained in the verse. The first verse seems to be praising the powers of herbs, for without them, the healer couldn't heal and the fortune teller could not foretell? But the last verse is very intriguing. When Saturn did live? So a shift back to an earlier period in history where all are seemingly equal, for we go on to a line about Kings and Beggars dining on the same simple plant materials. Roots in particular would come under the governance of Saturn. But I can't quite figure what the reference to Saturn means, because in this context he is cited as being a beneficial principle, yet traditionally would have been considered 'The Greater Malific'. I think we could probably do with a Hobbit to 'riddle me this'.

Bearheart, thanks for that, all very interesting. Yes, my Mother grew up in Ireland believing in the Fey and she said she saw one as a child with her grandad once. A little brown man who was there one moment and gone the next. Likewise an aunt of mine who was well travelled and very down to earth, said she saw a full size green skinned winged fairy while she was on a boat going down the Amazon. She said this fairy figure seemed to just slip off a branch and suddenly appeared in the jungle.. To dissapear again just as soon as she'd regained herself. Regards the Fairy Faith in Ireland, I think there are still a few who hold to the traditions of never harming a fairy tree or a fairy mound. But from what I hear, the younger generations are no longer holding to their grandparents folkloric traditions.
With particular regards to ancient traditions of singing to plants, it chimes something for me. I personally believe that all of Nature is itself in a condition of constant 'song' so to speak, the song of creation is in a way constantly surrounding us. But we must stop and listen deeply in order to hear. Anyone who has sat beneath a weeping willow beside a stream, as a breeze gently plays through the branches will have heard it, though maybe not recognised it in the same terms that I tend do :-)