Datura is a genus of nine species of highly poisonous, vespertine-flowering plants belonging to the nightshade family (Solanaceae). They are commonly known as thornapples or jimsonweeds, but are also known as devil's trumpets or mad apple (not to be confused with angel's trumpets, which are placed in the closely related genus Brugmansia). Other English common names include moonflower, devil's weed, and hell's bells. All species of Datura are extremely poisonous and psychoactive, especially their seeds and flowers, which can cause respiratory depression, arrhythmias, fever, delirium, hallucinations, anticholinergic toxidrome, psychosis, and death if taken internally.

The name Datura originates from the Hindi and Sanskrit words for "thorn-apple," with historical and cultural significance in Ayurveda and Hinduism, while the American term "jimsonweed" derives from its prevalence in Jamestown, Virginia, where it was called "Jamestown-Weed." Datura species are herbaceous annual or short-lived perennial plants up to 2 meters tall with trumpet-shaped flowers and spiny fruit capsules, historically used in traditional medicine, especially in India, where they hold cultural and ritual significance. Datura species classification is complex due to high variability and overlapping traits among species, with many "new species" later reclassified as local varieties or subspecies; most species are native to Mexico, though some have disputed native ranges outside the Americas, and the genus is closely related to Brugmansia and the recently established Trompettia.

Due to their effects and symptoms, Datura species have occasionally been used not only as poisons, but also as hallucinogens by various groups throughout history. Traditionally, their psychoactive administration has often been associated with witchcraft and sorcery or similar practices in many cultures, including the Western world. Certain common Datura species have also been used ritualistically as entheogens by some Native American groups.

Non-psychoactive use of plants in the genus is usually done for medicinal purposes, and the alkaloids present in some species have long been considered traditional medicines in both the New and Old Worlds due to the presence of the alkaloids scopolamine and atropine, which are also produced by plants associated with Old World medicine such as Hyoscyamus niger, Atropa belladonna, and Mandragora officinarum.

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