Heroin is derived from poppies. It is simply the product of acetylating the morphine isolated from the poppy plant. Also, the person you replied to was right,

Heroin is derived from poppies. It is simply the product of acetylating the morphine isolated from the poppy plant. Also, the person you replied to was right, the DEA is referring to heroin and cocaine, not cannabis. This is spelled out in the second paragraph of the executive summary in the pdf: "traditional plant-based drugs like cocaine and heroin".