You just have time to consider doing the 'Chelsea chop' on your perennials. You can do this in a number of ways - either cut back the whole plant by about one third or only chop back one third of the plants leaving some to flower earlier. Doing this encourages bushier growth, can stop the plants from flopping and can also extend the flowering period. Sedum, rudbeckia, echinacea, helenium, nepeta, phlox, asters will all respond well to this technique.
You can also cut back geraniums after they have flowered and you may get a second flush of flowers but you do need to water and feed them well.
Book recommendation:

The Well-Tended Perennial Garden: Planting and Pruning Techniques-Tracy DiSabato-Aust

Plant identification:

Centranthus ruber 'Albus' - which is the white form of red valerian. It has sprays of small white flowers in late spring and summer

Centranthus ruber 'Albus'
Valeriana officinalis - or common valerian - this is a tall and airy plant with pinkish- white small flowers with a nice vanilla scent

Valerian officinalis
Dinathus deltoides or Maiden pink is an evergreen perennial and has a mat of green foliage with clusters of cerise or white flowers. It is happy in chalk soil and can be grown in gravel gardens or with other alpines

Dianthus deltoides

Geranium 'Southease celestial' a lovely clump forming geranium with lavender blue flowers

Geranium 'Southease celestial'

Stipa gigantea -or Golden Oats is a striking evergreen grass, it has oat like flower heads in summer and can grow up to 6 feet. It likes well drained light soil and full sun

Activities in the garden this week