All freshwater pearls have been cultured, meaning that they were grown in pearl farms using science and technology rather than in nature by accident. This is where a trained technician implants an irritant in the mussel to stimulate the formation of a pearl. All freshwater pearls have been cultured, meaning that they were grown in pearl farms using science and technology rather than in nature by accident. This is where a trained technician implants an irritant in the mussel to stimulate the formation of a pearl.