My friend used miracle gro once. He also overwatered the plants a lot, which may have explained why they survived for a fairly long time (the plants were S. purpurea, S. rubra, S. minor, D. capensis, and N. ventrata). It may also have been the fact that most were fairly tolerant sarrs. In any case, the D. capensis and S. rubra eventually died, but the rest he still has. Again, the fertilizer may have been leached out by the excess water, but this is just one case.