Why does the one plant produce different flowers?

Look at these pictures.
These are the flowers that comes from only one Spiderwort.
(2012.5.7～2012.5.21)
Why does the one plant produce different flowers?

I planted my first Spiderwort 16years ago.
I've never seen such strange changings before Fukushima Daiichi nuclear disaster

 I know that the similar changing in Spiderwort are observed in our neighborhood.

Confirm

prepared  potted spider plant cultivated in the room
dig the Spiderwort (showed above)


wash the Spiderwort and plant Spiderwort in place of spider plant

bring the pot in a room

Observation

2012.5.22


2012.5.23


2012.5.24


3 days later, Spiderwort produced original designed flower



2012.5.26



2012.5.26

Learn from the results

Spiderwort was able to produce original flower again with using uncontaminated soil and cultivate in the room.

Changing in Spiderwort caused by Fukushima radiation.

mainly external exposure.