The hallucinogenic plant is a plant species indigenous to the Utopian moon, the only source of power for a Goa'uld who once attempted to rule there. Because a Furling transport portal guarded against anyone who might attempt to bring weapons into the realm, the Goa'uld decided the only way he could gain control was to administer a drug through the plants.
Whether this was the Goa'uld's attempt at ruling or an unusual experiment, the plan went wrong. Those who ingested the plants grew paranoid, hearing voices and doubting the intentions of friends. Even the Goa'uld itself was not spared when the villagers of the moon went mad, killing one another, and the host to the symbiote. According to Harry Maybourne, it tastes like arugula. (SG1: "Paradise Lost")