Based on all of my known science and lore there are two times for cutting foliage: when it looks bad and browns, for aesthetic reasons, and also in the early/late fall if desired for same reason.
Story is that Schreiner's in their early days cut foliage for shipping and it spread to others thinking it had to be cut in July/August, but it does not. Just getting out "spent" foliage is usually sufficient.
