That's pretty interesting. I remember in the orignal Teenage Mutant Ninja Turtles movie they found sunflowers growing over a toxic spill, but I always thought it was just to show that the spilled chemicals made things grow extra large, but it turns out it was just a lazy attempt at a cleanup.

Strangely enough, many years ago I read the following webcomic about something similar:

http://www.rhjunior.com/tales-of-the-questor-0587/

The story was about a racoon farmer trying to leech bauxite from the soil and created a plant to do it.

Where does the leached radiation go? What happens to the plant matter after the sunflowers die? Their seeds (and are the seeds viable?)?

I am curious.

It needs to be harvested and disposed of (i.e. locked away), but large scale agriculture makes this a solved problem.

I imagine that at least some of the seeds are viable, but pretty much the entire plant (seeds and all) is radioactive and needs to be collected, which for sunflowers means getting to them before they disperse their seeds to the winds.

Several people have talked about plants leaching "radiation out of the soil".

The plants are not separating isotopes. What they actually mean is the plants leach elements than happen to be radioactive. It would be nice if they said what elements.