The outright poisons — no safe home use
Foxglove. Lethal cardiac glycosides. In 1997 a supplier shipped digitalis in place of plantain and the FDA chased the mix-up across the country — that is how little margin this plant leaves. (Slifman et al., NEJM 1998; FDA warning letter 1997)
Deadly nightshade. Tropane alkaloids — atropine and scopolamine — in every part of the plant. Two women who mistook its leaves for wild lettuce ended in intensive care. (Boskabadi et al., Case Rep Neurol Med 2024)
Ergot. The alkaloids behind the "holy fire" — St. Anthony's Fire, the gangrenous and convulsive ergotism of the Middle Ages. The epidemic of 944–945 AD killed some 20,000 people in the Aquitaine region. (Schiff, Am J Pharm Educ 2006)
Pennyroyal. The oil is hepatotoxic, with a documented fatality measured in the toxicology literature — toxic metabolite levels in the blood, not rumor. (Anderson et al., Ann Intern Med 1996)
Chaparral. Of 18 adverse-event reports to the FDA in three years, 13 showed hepatotoxicity; some progressed to cirrhosis and fulminant liver failure requiring transplant. (Sheikh et al., Arch Intern Med 1997)
Blue cohosh. A newborn suffered myocardial infarction and profound heart failure after the mother took blue cohosh to promote contractions — the first described human fetal case, and one is enough. (Jones & Lawson, J Pediatr 1998)
Pokeweed. One state's poison centers logged 1,669 human exposures in twenty years, most of them children. The folk record does not make this plant food. (Woolum et al., Toxicon 2022)
Tansy and garden wormwood. Thujone — tansy oil averages about half thujone by content, and the poisoning record runs to convulsions. The regulators' statement records that thujone "has been regarded as a severe neurotoxicant." The risk-to-use ratio at home is poor. (WHO/JECFA; EMA thujone statement 2012)
Real medicine — which is exactly why it is refused
Hawthorn. The famous one, refused on purpose. Its honest indication is the heart, and heart conditions are never self-treated. The monograph record (leaf with flower) is acknowledged, not disputed. (Commission E)
Cinchona. Malaria is never self-treated. And quinine dosed casually is dangerous on the modern record: the FDA counted 38 serious cases — in a country where most quinine use was for leg cramps, not malaria — including hospitalizations and two deaths. (FDA Drug Safety Communication 2010)
Sweet wormwood. Artemisinin is supervised medicine. The WHO's standing position is that oral artemisinin alone should disappear from the market entirely, to protect the drug itself from resistance. (WHO; WHA60.18)
Snowdrop. Its alkaloid is the point: galantamine, isolated from this family, is a prescription drug for Alzheimer's disease. The pharmacy is where it belongs. (Heinrich & Teoh, J Ethnopharmacol 2004; FDA labeling)
Madagascar periwinkle. Its vinca alkaloids are chemotherapy. Vincristine's own label carries a fatal-route warning. This is an oncology drug's plant, not a remedy. (FDA labeling)
Sweet clover. Spoiled sweet clover hay bled cattle to death, and the chemistry behind that became dicoumarol and then warfarin. An anticoagulant is not a tea. (Link, Circulation 1959; Anaesth Intensive Care 2025)
Banned or restricted outright
Ephedra (ma huang). Banned by regulation: dietary supplements containing ephedrine alkaloids are adulterated by law. (21 CFR Part 119)
Sassafras. Safrole is banned as a food additive; food containing added sassafras oil is adulterated by the same regulation. (21 CFR 189.180)
Coca. Schedule II of the Controlled Substances Act. (21 CFR 1308.12)
Refused on the record's own terms
Arnica. The old record itself is the warning: King's prints "There is no known antidote to its poisonous influences." The one modern trial in its favor is acknowledged — the refusal is safety margin, not inefficacy. The bruise-and-sprain lane stays covered in our book by witch hazel and comfrey. (King's American Dispensatory 1898; WHO vol. 3; EMA; Widrig 2007)
Lobelia. The Eclectics' own pages: a single drop of its alkaloid solution "instantly vomited" a strong, healthy man, and "its injudicious use has, and might produce death." A remedy whose first act is violent emesis has no place in a home book. (King's American Dispensatory 1898)
Kava. Refused pending better data. Liver failures and transplants are on the record — "A total of 11 patients who used kava products had liver failure and underwent subsequent liver transplantation" — and the cause is still argued. Honest uncertainty is still a no. (CDC MMWR 2002)
Mugwort. A thujone-bearing cousin of tansy and wormwood, with a thin case for the kitchen. Refused conservatively. (EMA thujone statement 2012)
Refused for the plant's sake
Goldenseal. At-risk in the wild — United Plant Savers lists it so. The refusal is conservation: a remedy that costs the woods its population is not a remedy our book will teach. (United Plant Savers; WHO vol. 3; ESCOP)
Comfrey and arnica appear in the book as external-only entries; their internal use is refused inside their own pages, where the reasons are printed in full.
This page is educational, not medical advice. Never pick, prepare, or consume any plant on this list. Citations are printed in plain text by design; every claim above traces to a primary source read and archived before publication. Plants and their preparations can be unsuitable or unsafe — see a qualified practitioner for guidance about your own situation.