You can try making divisions, but the root system is dense and chunky, with a long taproot and doesn't really like being disturbed. To propagate by division, instead of digging up the whole plant, slice a piece of the plant off with a sharp knife. Make sure you get at least a ½ inch piece of the root. Pot it up and keep it moist. If you plan on trying to divide, do it early in the season, when the plants are small, and expect them to take a season or two to start blooming again.