well i play fallout alot and theres something in the game called a G.E.C.K garden of eden creation kit
The GECK builders had no idea what the post-nuclear world would be like, and they had no real way to anticipate it, despite their "thorough tests" (it's doubtful they gave it much thought, to be honest, considering how badly organized the Safehouse project alone was, not to mention the experimental nature of the Vaults) - still, it seems as if the seeds present in the GECK were viable for Vault 8.
The GECK's designers assumed that the Vault dwellers would know how to read and how to operate the various advanced technologies present in the Vault - they did not plan for the reduced knowledge of pre-War technologies common among wasteland tribals or other similar contingencies. They also did not plan on the FEV getting released into the wider world, or the fact that the Vault dwellers might be attacked by giant mutated scorpions, cockroaches or rats, either.
The GECK's seeds and soil supplements date themselves rather quickly, but "...the government subcommittees sponsoring the research and the GECK contractors (Future-Tec) weren't really concerned about that. They were 'relatively certain' the seeds would be viable in a post-nuclear environment. They had done 'thorough tests,' and 'all conclusions point to this as being the best option.' The GECKs are a miracle... a miracle that they work.
if a mutated geck thats has been in contact with fev forced evolutionary viruse which well is a mutatagen and if some one activated a mutated geck it would make dead matter live matter people into mutatants and some places might not be covered by the geck and so the plants would spread to some areas that are still ruins and not converted matter. that might of been what happened its a theory anyway