Calea zacatechichi, also known as Dream Herb, Cheech, and Bitter Grass, is a plant used by the indigenous Chontal of the Mexican state of Oaxaca for oneiromancy (a form of divination based on dreams.) The plant naturally occurs from southern Mexico to northern Costa Rica. It has been scientifically demonstrated that extracts of this plant increase reaction times and the frequency and/or recollection of dreams[1] versus placebo and diazepam. It is also employed by the Chontal people as a medicinal herb against gastrointestinal disorders, and is used as an appetizer, cathartic anti-dysentery remedy, and as a fever-reducing agent.

The Chontal medicine men, who assert that this plant is capable of "clarifying the senses" causing euphoria, call it thle-pela-kano, meaning "leaf of God". Whenever they desire to know the cause of an illness or the location of a distant or lost person, the common ritual is to smoke a cigarette, whilst drinking a tea, both made of Calea Zacatechichi, right before going to sleep. Some also report placing the leaf of God under their pillow before sleeping. Reportedly, the answer to the question comes in a dream.[2]

Preparation and dosage: Crushed dried leaves are steeped in hot water, and the resulting tea is drunk slowly, after which the user lies down in a quiet place and smokes a cigarette of the dried leaves of the same plant. The human dose for divinatory purposes reported by the Chontal people is a handful of dried plant, but effects can be felt with as little as two to three grams of dried leaf matter. The user knows that he or she has taken a large enough dose when a sense of tranquility and drowsiness is experienced and when he or she hears the beats of his or her own heart and pulse. Calea is an extremely bitter herb and is known to induce strong nausea when drunk. Many users prefer to smoke it rather than drinking the tea. Alternatively alcoholic tinctures and placing the leaf matter in algae capsules can be as effective as tea while being much less bitter and much more palatable. There are no reports of hangover or other undesirable side effects. Many report an extremely mild cannabis like state of relaxation from smoking calea leaf or taking calea tincture.

Law: Calea zacatechichi is an unscheduled substance in the United States, meaning that it is completely legal to grow and sell. However, Louisiana State Act 159 makes the substance illegal to grow, cultivate, harvest or sell in Louisiana if intended for ingestion. The act applies to more than 40 types of plants.[3]

Tennessee proposed a bill that would have made many "hallucinogenic" plants, including Calea zacatechichi, illegal when "intended for human consumption," but the law was changed to ban only Salvia divinorum and Damiana (Turnera Diffusa).[4]