The invention relates to a method for producing a stably reproducing poppy plant of Papaver somniferum having thebaine and oripavine constituting about 50% by weight or greater of the alkaloid combination consisting of morphine, codeine, thebaine and oripavine, the method comprising the steps of:a) exposing at least one poppy seed of Papaver somniferum to a mutagenizing agent,b) growing the at least one poppy seed to produce a plant bearing a leaf or an immature poppy capsule, optionally through multiple self-fertilized generations,c) sampling the leaf or poppy capsule for the presence of thebaine, oripavine, morphine and codeine, andd) repeating steps a) to c) until a poppy plant of Papaver somniferum is obtained having thebaine and oripavine constituting about 50% by weight or greater of the alkaloid combination consisting of morphine, codeine, thebaine and oripavine, and to plants obtainable by this method.
