content: This is a natural mutation that occurs in over 100 plant species called Fasciation. Although rare, it has been observed in plants from all over the world, including those with no damaged nuclear facilities. It has been observed in daisies elsewhere. As I have pointed out in other comments also, the radiation level reported (0.5 microsieverts) is EXTREMELY low, and is really not higher than most background radiation levels. If you have a concrete pad in your basement, you have higher radiation levels down there.