Take the spent heads off peonies and even perhaps a foot of upper stem from the tall varieties, so that the plant is less inclined to splay in the rain.
Keep nipping off the spent flower stems of Osteospermum to keep further flowers coming.
Do the same but with secateurs or shears to the mats of the rock rose, Helianthemum, a sprawling little shrub, which, if its flower stems are taken back by a few inches to some promising buds now, will happily flower again.
If you are using fungicides on roses against blackspot, etc, use different fungicides to reduce the chance of immunity.
Feed box hedges and topiary to keep them growing strongly and a rich green.