3. Fly Agaric Mushroom
The fly agaric mushroom has a pretty distinctive appearance and is widely recognized. The mushroom is officially classified as poisonous, although the amount of deaths from the species have been relatively few. The species has also been associated with a hallucinogenic effect, as the result of the compound muscimol.
Peyote is a particularly well-known psychoactive plant and this effect is largely the result of the compound mescaline. Peyote has strong cultural significance for Native Americans and is sometimes used for its psychoactive properties and sometimes for potential curative properties. The use of peyote is generally illegal in the United States, although there are some exceptions for members of the Native American Church and for religious ceremonies.
The drug opium is produced from dried latex that comes from the opium poppy. Because of this, poppies are frequently grown specifically for the production of opium, often in large fields. Opium is heavily regulated and is often used as a precursor to other modern drugs. However, the flowers of the species are pretty and popular, which makes them common choices for gardens.
Bonus! Himalayan Giant Honey Bees Making Psychedelic Honey
Not even joking. It's also called “magic honey” or “mad honey”. It's properties come from the fact that the bees pollenate psychoactive flowers. Learn more about the people and how they collect/use the honey.