It's easy to get impatient when the flower stalks start to flop in midsummer, but chopping them back early cuts off photosynthesis right when the rhizomes need it most. The plant's leaves might look rough around this time, but they're busy sending energy underground. One big reason your iris plants are having trouble flowering could be because you've neglected fall cleanup. Fungal spores and bacteria also thrive in dead leaves, especially once fall rains set in. Clearing out the mess in fall shuts down those hiding places and keeps your beds healthier with a lot less effort later.