In z 6, northern IL, pretty much clay here. My best flowering shade plants are: Heartleaf Aster, 4-5', pale lavender in early fall -native; Woodland Aster 18", white in late summer to early fall; Tricyrtis, any, white/purple from 18" to 3', late summer to early fall; Pulmonaria, 12", pink, purple or blue in spring then nice foliage; Spigelia, 18"+ with great red flowers in summer -native; Rabdosia, 5' purple in fall, (may be hard to find; Lysimachia, aka Gooseneck which spreads a lot will do fine in shade, just a bit slower and shorter, 2-3' white in summer; Anemones-huge variety, some spread a little, some a lot, spring or fall; Astilbe, pinks and white for summer and not too dry; Stylophorum; Saruma; ..........how much room do you have? Becky Daisy also does well in quite a bit of shade, and Chelone glabra, pink Turtlehead, 4' mid-late summer will spread moderately; Campanula Americana, native with blue flowers, 4' will reseed but not crazy for me; September Charm Anemone gets 4-5', pale pink, late summer-fall and will take over and hard to get rid of but will blend with other tall plants and not drowned them out, (for me); Persicaria Firetail blooms dk pink from mid summer-frost, 4-5' and grows moderately to form a large clump; also Tradescantia; Smilacina; Actea..... That's about all I have. Hope something strikes your fancy! I'm sure other will chime in.