Campanula cochlearifolia 'Bavaria Blue'

A creeping rhizomatous perennial, making a compact mat of small, rounded leaves with blue, bell-shaped flowers in summer. A selected, very compact form. 10cm x 30cm wide  Excellent in rock gardens or troughs. Spreads, so to confine it if you feel the need to protect more feeble growers, plant within a ring of lawn edging or bottomless pot hidden just under gravel if you want a discrete mound. Or trap it between a couple of large rocks, which looks brilliant. Imagine if you could organise this rock scenario...

Jerzy Opioła, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

Single flower: Teun Spaans, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons