I have quite a few Echinacea Purpurea, Purple Coneflowers, that start to bloom in the later part of summer, right into the fall. They make a definite transition in the seasons.

"The last of Summer is Delight --
Deterred by Retrospect.
'Tis Ecstasy's revealed Review --
Enchantment's Syndicate.
To meet it -- nameless as it is --
Without celestial Mail --
Audacious as without a Knock
To walk within the Veil."
- Emily Dickinson, The Last of Summer is Delight