Echinacea thrives in clay soil. Grows to 2 to 5 ft tall in full sun to part shade, Zones 3-8. Piet oudolf planting at Dreampark, Enkoping, Sweden: Echinacea purpurea 'magnus', scutellaria incana, astilbe chinensis var taquetii 'purpurlanze'. By Clive Nichols.
Astilbe : this perennial is a great shade plant with dense foliage + feathery, summer blooms for a shade garden. aka False Spirea, False Goat's Beard. Astilbe is native to Asia and North America. Blooms in June-July. Colors include pink, red, white, purple and peach. Plants grow 18" to as much as 5 feet. There is a dwarf variety that grows about 6". Pairs well with hydrangeas, hostas, & ferns. by DeeDeeBean
Stipa Tenuissima - The beautiful evergreen feather grasses (Stipa tenuissima) stimulate through vision; sound and feel. They are a wonderful base to plant more structural plants through such as Alliums; Crocosmia and Agapanthus