Dangerous Garden by David Stuart: Quest for Plants to Change Our Lives

frankbeswick, Please accept my apologies for the delay ... and the misinformation.
The Food & Drug Administration, not the United States Department of Agriculture, in 2001, not 2007, advised against external and internal use of comfrey, respectively on open wounds and because of cancer and liver damage.
I don't seem to be able to access the advisory even though I have the source information: FDA. 2001. FDA advises dietary supplement manfacturers to remove comfrey products from the market. USFDA, Center for Food Safety and Applied Nutrition.
A 2005-released study -- Mutagenicity of comfrey (Symphytum Officinale) in rat liver, by N Mei, L. Guo, PP Fu, RH Heflich and T Chen -- in the British Journal of Cancer 92(5): 873-875 -- gives the FDA URL, which does not bring it up, at least for me.
The above-mentioned study likewise lists in its bibliography Rode, D. November 2002. Comfrey toxicity revisited. Trends in Pharmacological Sciences 23(11): 497-499. The latter notes that "The conclusion that comfrey is not safe for internal use in humans is primarily based on studies in which high levels of purified PAs [pyrrolizidine alkaloids] were administered to rodents.Systematic toxicity testing or clinical trials have not been performed. Although PA poisoning in humans can occur, this is most commonly a consequence of consumption of plants other than comfrey." She suggests that "Clearly, the risk of hepatic damage during treatment with comfrey will be influenced by its source, the amount consumed, the duration of treatment, and the health and nutritional status of the patient." Rode states that low-protein diets facilitate the PA toxicity that high-protein diets minimize.

Thanks Derdriu.I await your response.As one who suffered liver disease as a child I have to be careful.

frankbeswick, The fuss happened about 10 years ago because of liver damage from ingestion. But the USDA then also mentioned that external applications can be problematic near or on broken skin. I will check and get back about this since I'm writing from memory, without specifics at hand.

:)

My doctor recommended comfrey oil for my troubled knee joints, and it has been beneficial when rubbed in. What was the USDA warning about it?

Mira, Me neither, I don't watch much television.
Elementary is considered an American series even though there is U.K. involvement, most noticeably with English actor Jonny Lee Miller as a Sherlock Holmes updated to 21st-century New York City. I like the way that it's so educationally entertaining, with episodes on animals, artwork, fossils and plants.

I may have seen parts of the Elementary series on TV. I don't watch much TV. I do, however, see, borrow DVDs with certain series from the British library.

Mira, Does Romania carry the Elementary procedural drama series episodes with Jonny Lee Miller, Lucy Liu, Jon Michael Hill and Aidan Quinn? The sixth season atypically is running from May through September. Monday's episode Aug. 27, 2018, plotted around death-inducing, mind-controlling, mind-expanding scopolamine from the dried, powdered seeds of Brugmansia (Angel's trumpets, Devil's breath) species: scary!
The plant puzzles make great gifts, for others and -- ;-D -- to oneself.
I think of comfrey for organic fertilizer. In its herbal uses, which I don't use anyway, comfrey was initially a surprise but then I remembered the to-do about USDA warning about external and internal applications.

This is so interesting, and I only know a few of these plants. I was surprised to learn how rhubarb was used throughout the centuries! Also, I didn't know comfrey was poisonous. In fact, didn't know what that plant was called until I saw the photo here. So thanks :)

I like the idea of a puzzle for plants :)

frankbeswick, Excellent observation! Alternative, homeopathic, modern and traditional medicine, like surgery, call for a steady hand.