Campanula cochleariifolia ‘Bavaria Blue’. Fairy Thimble Bellflower. USDA Zone: 2-9. Plant number: 1.111.090. One of the most charming of the popular perennial Bellflowers. The Fairy Thimble forms a low mat of tiny green leaves, bearing loads of tiny little dangling lavender-blue bells in early summer. Delightful growing among rocks, on walls, and between paving stones.