Some believe that everything what grows on Earth has only Earth's origin. Some do not.
Here is an excerpt from the "Songs of Malantor" book that proposes a different view:

Early in the development of Earth's vegetative cover, plant species with different healing properties were brought by extraterrestial intelligences to provide budding humanity with easily obtained curative agents. It is particularly unfortunate that ... spiritually immature people are short-sightly usurping the natural properties of mind-altering plants for monetary gain. Many are beginning to view nature's greatest gifts as a means to momentarily enhance, deaden, or otherwise escape the physical, mental, and emotional pain that permeates "civilized" society.

...we recommend choices that promote health and emotional well-being through the appropriate use of psychedelic drugs and medicinal herbs. A critical, thorough study of literature available on the ancient uses of medicinal herbs and aromatherapy is recommended for those who are drawn to alternative healing arts.