The Commentary on the Convention on Psychotropic Substances notes that while many plant-derived chemicals are controlled by the treaty, the plants themselves are not:
The term "synthetic" appears to refer to a psychotropic substance manufactured by a process of full chemical synthesis.
One may also assume that the authors of the Vienna Convention intended to apply the term "natural material" to parts of a plant which constitute a psychotropic substance, and the term "natural psychotropic substance" to a substance obtained directly from a plant by some process of manufacturing which was relatively simple, and in any event much simpler than a process of full chemical synthesis.

(...)
Cultivation of plants for the purpose of obtaining psychotropic substances or raw materials for the manufacture of such substances is not "manufacture" in the sense of Article 1, paragraph (i).
Many provisions of the Vienna Convention governing psychotropic substances would be unsuitable for application to cultivation.
The harvesting of psychotropic substances, i.e. separation of such substances from the plants from which they are obtained, is "manufacture".

(...)
The cultivation of plants from which psychotropic substances are obtained is not controlled by the Vienna Convention. (...)
Neither the crown (fruit, mescal button) of the Peyote cactus nor the roots of the plant Mimosa hostilis nor Psilocybe mushrooms themselves are included in Schedule 1, but only their respective principles, Mescaline, DMT and Psilocybin.

Mexico, in particular, argued that "production" of psychotropic drugs should not apply to wild-growing plants such as peyote cacti or psilocybin mushrooms.
The Bulletin on Narcotics noted that "Mexico could not undertake to eradicate or destroy these plants".
Compared to the Single Convention on Narcotic Drugs (which calls for "uprooting of all coca bushes which grow wild" and governmental licensing, purchasing, and wholesaling of licit opium, coca, and cannabis crops), the Convention on Psychotropic Substances devotes few words to the subject of psychoactive plants.

On 2 July 1987, the United States Assistant Secretary of Health recommended that the Drug Enforcement Administration initiate scheduling action under the Controlled Substances Act in order to implement restrictions required by cathinone's Schedule I status under the Convention.
The 1993 DEA rule placing cathinone in the CSA's Schedule I noted that it was effectively also banning khat:
Cathinone is the major psychoactive component of the plant Catha edulis (khat).
The young leaves of khat are chewed for a stimulant effect.
Enactment of this rule results in the placement of any material which contains cathinone into Schedule I.
The Commentary on the Convention on Psychotropic Substances notes that while many plant-derived chemicals are controlled by the treaty, the plants themselves are not:
The term "synthetic" appears to refer to a psychotropic substance manufactured by a process of full chemical synthesis. One may also assume that the authors of the Vienna Convention intended to apply the term "natural material" to parts of a plant which constitute a psychotropic substance, and the term "natural psychotropic substance" to a substance obtained directly from a plant by some process of manufacturing which was relatively simple, and in any event much simpler than a process of full chemical synthesis.
(...)
Cultivation of plants for the purpose of obtaining psychotropic substances or raw materials for the manufacture of such substances is not "manufacture" in the sense of Article 1, paragraph (i). Many provisions of the Vienna Convention governing psychotropic substances would be unsuitable for application to cultivation. The harvesting of psychotropic substances, i.e. separation of such substances from the plants from which they are obtained, is "manufacture".
(...)
The cultivation of plants from which psychotropic substances are obtained is not controlled by the Vienna Convention. (...) Neither the crown (fruit, mescal button) of the Peyote cactus nor the roots of the plant Mimosa hostilis nor Psilocybe mushrooms themselves are included in Schedule 1, but only their respective principles, Mescaline, DMT and Psilocybin.
Mexico, in particular, argued that "production" of psychotropic drugs should not apply to wild-growing plants such as peyote cacti or psilocybin mushrooms. The Bulletin on Narcotics noted that "Mexico could not undertake to eradicate or destroy these plants". Compared to the Single Convention on Narcotic Drugs (which calls for "uprooting of all coca bushes which grow wild" and governmental licensing, purchasing, and wholesaling of licit opium, coca, and cannabis crops), the Convention on Psychotropic Substances devotes few words to the subject of psychoactive plants.
On 2 July 1987, the United States Assistant Secretary of Health recommended that the Drug Enforcement Administration initiate scheduling action under the Controlled Substances Act in order to implement restrictions required by cathinone's Schedule I status under the Convention. The 1993 DEA rule placing cathinone in the CSA's Schedule I noted that it was effectively also banning khat:
Cathinone is the major psychoactive component of the plant Catha edulis (khat). The young leaves of khat are chewed for a stimulant effect. Enactment of this rule results in the placement of any material which contains cathinone into Schedule I.
Convention on Psychotropic Substances