Campanula portenschlagiana

Campanula portenschlagiana syn. C. muralis, is a species of flowering plant in the family Campanulaceae, native to the Dalmatian Mountains in Croatia. It is a vigorous, low-growing, mound-forming evergreen perennial with deep purple flowers in summer. Common names include Dalmatian bellflower, Adria bellflower and wall bellflower.

Description
The plant forms a mat of foliage about 10 cm (4 in) high and 50 cm (20 in) or more wide, with many heart- or kidney-shaped leaves. Deep purple or blue, funnel-shaped, 5-petalled flowers, 2 cm long, are borne in profusion, completely covering the plant from mid- to late summer.

Flowers may be pollinated by beetles, flies, bees and butterflies, but are also capable of self-pollinating.

C. portenschlagiana is a low-growing perennial quickly forming an evergreen mat of small, rounded leaves.
As an alpine plant, it requires sharp drainage, so is suitable for an alpine garden, rock garden, or as groundcover, in sun or partial shade. Given suitable conditions, it will rapidly colonize cracks and crevices in walls and pavements. It is hardy at least to USDA hardiness zone 4 (−30 °F or −34 °C).