Many years ago a gardening friend passed along a few seedlings of C. alliarifolia which has proven to be a long-lasting standard in my garden. While not a floral knockout like some bellflowers, it is still desirable for its felted, heart-shaped leaves and loose spikes of cream-white, hairy-fringed flowers that are produced over a long period from June to September. This clumper reaches 45 to 60 cm and is best planted in groups nearer the front of the border. Subsequently I read about a blue flowered C. alliarifolia look-alike called C. sarmatica. I was lucky to track down seeds, which germinated with no fuss. The resulting plants formed clumps of crinkled, grey-felted leaves and loose spikes of lovely pale lavender-blue bells. This species reaches to 50 cm and is also best planted as groups towards the front of the border. And to complete this set, I also grew from seed C. kolenatiana, another fuzzy-leaved species, this one with violet-blue flowers.
Shown above are close-ups of C. alliarifolia, C. sarmatica and C. kolenatiana
The pale or European bellflower, C. bononiensis, looks very similar to the cursed C. rapunculoides but is not invasive like the latter species. It produces upright stems to 90 cm with light lavender-blue flowers mid-summer. From Hungary comes C. grossekii, a 100 cm species with hairy-fringed, violet-blue flowers. Don't confuse this species with C. grossheimii, which is a rock garden subject that looks like a half-sized version of C. sarmatica. The lavender bellflower, C. longistyla, is an elegant species reaching 60 cm. In this species, the styles extend well beyond the ‘bell'. It is apt to be a short-lived species so allow it to self-seed or collect seeds. 'Isabella' is a dwarf selection only 20 cm and literally smothers itself in flowers.
A close-up of C. longistyla
There are four biennial bellflowers suitable for the perennial border, one well-known, the others less so. The former is the popular Canterbury bell, C. medium. Like foxgloves, this species produces a rosette of evergreen leaves in the first season then produces a flower stem in the second. In the case of Canterbury bells, the stout stem arises 75 to 90 cm and produces impressive dense clusters of large outward-facing bells in shades of white, blue, purple and pink. Perhaps most popular is the 'Cup and Saucer' types whose flowers consist of a bell within a bell. The chimney bellflower, C. pyramidalis, is technically a short-lived perennial but perhaps best treated as a biennial. In its second season, this species produces very tall (up to 1.5 m), narrow spikes of white or violet-blue, outward-facing, star-like bells. To make the best impact, plant them in groups. The most unusual biennial species is C. thyrsoides. When blooming, the stems reach 45 to 75 cm but what is most unique are its upward-facing, straw-yellow flowers, a colour unique among bellflowers. Finally there is C. rapunculus, aka rampion, which produces stems to 1 m and open sprays of small blue, outward-facing bells (the flowers appear similar to C. lactiflora). This species is not to be confused with C. rapunculoides which is perennial. Historically, C. rapunculus was the only bellflower used as a vegetable. In this case, the thick carrot-like taproot was used as a root vegetable.
Above are C. thrysiflora, C. pyramidalis and C. rapunculus
Some examples of C. medium
A final species of note is the lovely C. latiloba, a much more refined version of the peach-leaved bellflower. The flowers of this species are produced in a dense spike on relatively stout stems. The individual flowers and leaves looks very-much like C. persicifolia but plants are much more resistant to wind and rain and have more impact in the border. However, for some reason, this popular European species has never made much of an appearance in North America. I cannot find any reason why it isn't widely grown on this side of the Atlantic. I'm sure this attractive species would be a valuable addition to the wide array of bellflowers which grace the herbaceous borders of North American gardeners.
I would like to thank the following people for the use of their pictures: bootandall (C. trachelium 'Alba;), Calif_Sue (C. pyramidalis), echoes (double C. trachelium), htop (C. longistyla), Kell (C. medium), poppysue (C. medium) and Weezingreens (C. medium).