You could try The Grete Herball, which is available from
Gutenberg as a section of a larger work. You'll be interested in Chapter II. The Grete Herball is a translation into English of Le Grant Herbier, which is the first major herbal published in France (1486, author unknown).You can view the woodcut images in the book from
The Historical Medical Library. I have not been able to find a text of the French version, but you might if you read French.
That is the
only book that I was able to find, though -- and I had to dig through perhaps 30 - 40 English texts before I found it, which seems really strange. I think there might be a couple things going on, besides the propensity for French works to be published in French, which I don't read.
Up until 2016 you could have tried Place de Clichy Herboristerie, which is (or was) a French herb shop which opened in France in 1880. It is currently illegal to practice herbal medicine without registering with the Pharmaceutical Society, and the owners, although having doctorates in Pharmacy, were placed under injunction, fined and potentially faced jail time. I wasn't able to find a good source in English but here is article from
Le Parisien in case it interests you (the translation from Google isn't perfect but it gives the idea). Just thought it could be related to your difficulty.
The other issue is that it might be difficult, before the 15th century, to separate "French" herbalism from "Latin" herbalism, at least from University educated pharmaceutical practitioners. French is much closer to Latin than English is, and I seem to recall (though I have no source) that Latin remained the primary written language of the University there much longer than it did in England. Also, because of the propensity for authors to plagiarize massive sections of other author's works, there probably isn't as much difference between Roman/Italian and French herbalism as you might hope or expect. In fact, more than half of Le Grant Herbier is lifted from an older work, Circa Instans, an Italian work, a practice which was basically ubiquitous during the Middle Ages. Not to say that there isn't a uniquely French folk tradition of herbalism, but you're unlikely to find that in books, especially published 1800 or earlier, because those traditions tend toward oral dissemination rather than publication.
