text: is marijuana the only illegal plant in the united states???? does anyone know all the countries it is now legal in?? hemlock is also classified as a poison.  furthermore, it is illegal to import or possess any number of plants.  marijuana is the only plant classified as a controlled substance, i believe, but it is certainly not the only plant that may not be imported or possessed.   it remains illegal in most countries.  even in the netherlands where it is openly smoked in coffee shops, that is only by benign neglect and it is still illegal in the netherlands.