Kingdom: Plantae
(Unranked): Angiosperms
(Unranked): Eudicots
(Unranked): Asterids
Order: Asterales
Family: Campanulaceae
Subfamily: Campanuloideae
Genus: Campanula
Species Campanula portenschlagiana
Synonym: Campanula muralis
Common names: Wall Bellflower, Dalmatian Bellflower, Adria Bellflower, Wall Bell Flower, Hoffman’s Blue Bellflower.
Campanula portenschlagiana is a species of flowering plant native to the Dalmatian Mountains in Croatia. It is vigorous, spreading ground plant which forms a mat of foliage about 10 cm high and 50 cm 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 early to late summer. Its flowers may be pollinated by beetles, flies, bees and butterflies, but are also capable of self-pollinating. Given suitable conditions, it will rapidly colonise cracks and crevices in walls and pavements.
Though not a problem it has escaped from gardens.
Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/