Materia Medica

Tansy (Tanacetum vulgare) — Common Tansy, Bitter Buttons, Golden Buttons
Common tansy is a historic European herb with old culinary, antiparasitic and household uses, but modern internal use is limited by unpredictable essential-oil chemotypes and thujone neurotoxicity. This guide separates true Tanacetum vulgare from tansy ragwort and feverfew, explains U.S. food restrictions, and reviews identification and safety. Read more...
Tea Tree (Melaleuca alternifolia) — Narrow-Leaved Paperbark, Snow-in-Summer
Tea tree oil is a steam-distilled topical essential oil from Melaleuca alternifolia with human research for acne and some superficial fungal conditions. This guide separates topical evidence from laboratory claims, explains why the oil should not be swallowed, and covers oxidation, contact allergy, storage and the debated endocrine-disruption claim. Read more...
Illustrated thunder god vine with the labels Thunder God Vine and Tripterygium wilfordii at the top; not a field identification photograph
Thunder God Vine (Tripterygium wilfordii) — Lei Gong Teng, Yellow Vine
Thunder god vine (Tripterygium wilfordii), or Lei Gong Teng, has clinical research in rheumatoid arthritis and kidney disease but serious toxicity risks. Explore its traditional context, research, plant-part dangers, fertility... Read more...
Tobacco (Nicotiana tabacum) — Common Tobacco, Virginia Tobacco
Nicotiana tabacum is the principal cultivated tobacco species, a culturally important American plant containing highly addictive and potentially toxic nicotine. This guide covers botany and traditional context, nicotine poisoning, green tobacco sickness from skin exposure, the health effects of tobacco use, and current U.S. tobacco-product regulation without providing smoking, curing or nicotine-extraction instructions. Read more...
Tonka Bean (Dipteryx odorata) — Coumara Nut, Cumaru
Tonka bean is the intensely fragrant seed of the South American tree Dipteryx odorata and one of the original natural sources of coumarin. This guide reviews its botany, fragrance and traditional uses, explains human coumarin hepatotoxicity, and states the U.S. food restriction accurately: foods containing added coumarin from tonka beans or tonka extract are deemed adulterated. Read more...
Usnea (Usnea spp.) — Old Man's Beard, Tree Moss
Usnea is a genus of fruticose beard lichens with a long traditional-use history and genuine antimicrobial chemistry, especially around the lichen metabolite usnic acid. This guide explains lichen identity, identification, traditional use, the limits of modern evidence, and the serious liver-safety history of concentrated oral usnic acid. Read more...
Wahoo (Euonymus atropurpureus) — Eastern Wahoo, Burning Bush
Eastern wahoo is a native North American shrub or small tree with striking pink-red fruit and a place in historical American materia medica. Because all parts can be poisonous if ingested and may cause gastrointestinal and cardiac effects, this article focuses on identification, history, ecology and safety rather than home dosing. Read more...
Wild Cherry (Prunus serotina) — Black Cherry, Wild Black Cherry
Wild cherry bark comes from the North American black cherry, Prunus serotina, whose dried bark has a long cough-syrup tradition. This guide separates medicinal bark from edible pitted fruit and from cyanogenic pits, leaves and twigs, while reviewing the limited modern human evidence and important safety issues. Read more...
Wild Indigo (Baptisia tinctoria) — Yellow Wild Indigo, Horsefly Weed
Wild indigo, Baptisia tinctoria, is a yellow-flowered eastern North American perennial with dye, ethnobotanical and historic Eclectic-medicine uses. This guide separates that history from modern evidence, explains quinolizidine-alkaloid safety, and clarifies why common-cold research on multi-herb combinations does not prove Baptisia works alone. Read more...
Wild Lettuce (Lactuca virosa) — Bitter Lettuce, Opium Lettuce
Wild lettuce, Lactuca virosa, has a long European history as a bitter sedative and analgesic herb whose dried milky latex was called lactucarium or “lettuce opium.” This guide explains why that nickname is misleading, reviews lactucin and lactucopicrin research, documented human toxicity, identification, and safety without providing home extraction or dosing instructions. Read more...
Wild Yam (Dioscorea villosa) — Colic Root, Rheumatism Root
Wild yam, Dioscorea villosa, is a native North American medicinal vine whose rhizome contains steroidal saponins including diosgenin. This guide explains its traditional use, the pharmaceutical history of diosgenin, the persistent but incorrect “natural progesterone” claim, menopause research, identification, sourcing and safety. Read more...
Wintergreen (Gaultheria procumbens) — Teaberry, Checkerberry, Boxberry
Wintergreen, Gaultheria procumbens, is an eastern North American evergreen groundcover whose leaves and oil are strongly associated with methyl salicylate. This guide separates traditional leaf and berry use from concentrated wintergreen oil, reviews topical pain traditions and modern toxicology, and explains why essential-oil ingestion or excessive topical exposure can cause serious salicylate poisoning. Read more...