If those plants really couldn't be killed, then no matter how many ideas those Deities had, it would be hard for them to make any impact. But now that the plants can indeed be killed, Zhou Tian's subsequent actions would certainly have room to make an impact.
It can be imagined that, considering the circumstances those Deities were in, if they took action with all their strength, they might not be able to completely eradicate the plants at the root. However, 'killing' the plants multiple times wouldn't be an issue. After all, the plants' fear of fire remains unchanged. As long as flames are used to attack their bodies, it wouldn't be a problem to kill those plants.
