I solemnly swear that the Flora will not seed their cells into other organisms.

The Flora start to shut down and go into a dormant state to conserve energy when kept in temperatures below freezing for too long. An EMP would stop them for a few seconds before they absorb more heat and reactivate themselves. Individual cells can be destroyed by just about anything, but the heat most forms of destruction release is usually enough to fuel the creation of new cells. Extreme cold and black holes are really the only way to be sure. Containment would be the more realistic option, and that could be followed up with extreme cold.

I'm not that surprised that there's similar stuff out there. Nothing is completely unique anymore.