Bellflower, the biggest of the Campanula strains, is well suited to the Arboretum. It does not grow as tall as in a fertilised perennial bed and therefore remains more upright. It flowers in July, and longer in the semi-shade of the forest garden. It grows abundantly at Mustila at the western end of the Southern Slope.
In perennial soil the bellflower grows to over a metre. After a heavy summer shower, the stems may be so heavy that they fall over unless supported. The flowers are usually blue, bordering on purple, and sometimes white.
In time, bellflower grows into a fine, sturdy group as nutrients accumulate in the thick white roots. Bellflower is also self-seeding, but does not spread like a weed, even though the pod has lots of little seeds.