This grower is sure of this plant identification.
Blue and white forms
Carpathian bellflower, Carpathian harebell, Tussock bellflower, Bellflower
Campanula carpatica (Carpathian bellflower). This is a small clump forming, deciduous perennial which is native to Europe. It will bear bell-shaped white-green blue-purple flowers and toothed dark green foliage.
They will prefer cool nights and light shade in hot areas along with neutral to alkaline, moist, well drained soil.
Ground cover, walls, rock gardens, border. Summer interest.