Agastache Blue Fortune. It begins blooming in mid July and will continue through the fall. A favorite of bees and smaller butterflies.
In the past I've had some disease problems with coneflowers but not this year. I should have cut these plants back by about half in early June. That would have prevented the tendency to bend that they have in very wet years. Never the less, the coneflowers are doing exceptionally well this summer and deserve the award. They also attract bees and butterflies which is a big plus.
Coreopsis Moonbeam sometimes tends to take a back seat to the showier bloomers but it's value comes as a filler covering the ankles of taller plants. Some of the coreopsis are brighter yellow but I like the muted, buttery shade of Moonbeam.
Daylilies, every imaginable color and shape. They provide a huge return in blooms for the small investment in space they require. Night Embers below has a pretty white edging around its double petals. A dull red in full sunshine it looks much darker in the shade or on cloudy days.
In my garden, hardy Geranium Rozanne serves the same purpose as coreopsis Moonbeam. It looks nice around the feet of taller plants and provides constant color. She also works well planted with spring blooming bulbs.
Rudbeckia deserves its popularity. It looks great in small clumps with other plants and in huge drifts by itself. It has the informal charm of the sunflower with a much longer bloom time. Attractive to some butterflies.
Gaillardia, I've read that this plant literally blooms itself to death. Usually not a long lived perennial for that very reason. Even when treated like an annual and replace every year or so it's worth the small trouble and expense. New colors and sizes are marketed frequently, so if Goblin is too bright for your taste, choose the wine red or the sunny yellow instead.
Last my favorite garden plant, phlox paniculata, Volcano garden phlox. Not a speck of diseased foliage on this long blooming plant. Twice the flower power of David with a much longer bloom period. Only two thirds as tall as David so Volcano never flops or requires staking or caging. Best of all it is a magnet for Tiger Swallowtail butterflies.