Some flowers will favour leaf, if you feed them, at the expense of flower. So they will bloom much better in poor soil, nasturtiums being a well-known example - maybe other people can speak from experience about other plants that are best if you treat them mean? I have a primrose this spring, that I have kept in the too-small pot it came in, and have occasionally forgotten to water till it collapsed; it has flowered unbelievably thickly - and after each drought, has flowered all over again. When it stops flowering, I'll plant it out and *then* feed it, it will deserve it... :)