I have self sown seedlings from Orientals.
I also believe the original plant self sowes close to the main plant creating a clump. I might be wrong about this tho.
There are certain varieties of OP's that are hard to get rid of here. I have dug the dormant plants in August for transplanting and find new shoots come up in the same spot. These are caused by pieces of roots left behind. I think it was Coral Reef that expanded that way.