Bellflowers for the Border
There is no doubt that the genus Campanula, commonly called bellflowers, are an important constituent to any garden. While most gardeners recognize them as blue, bell-shaped flowers, they do come in white, cream, purple, pink, yellow as well as varying shades of blue. The flowers may be upward, outward or downward-facing and while mostly bell-shaped some can be star-like. The plant habits vary considerably from mat-like dwarfs under a few centimetres to giants towering to 2m or more. That is not surprising when you consider there are over 300 species and numerous hybrids. So, I think it is safe to say, there is a bellflower suitable for any garden be it a perennial border, cottage garden or rock garden.
In their native haunts, they are found exclusively in the northern hemisphere, with most species centred around the Mediterranean region. Most of them are quite hardy, although there are a few more tender species. As a group, they prefer sunny sites with well-drained soils. However, a few will tolerate considerable shade. Most hail from limestone regions so appreciate a soil that has a neutral to alkaline pH. They are care-free with few disease or insect pests, with the exception of slugs and snails who relish the blossoms of the dwarf types.
In the larger picture, bellflowers fall into one of two categories; dwarf, rock garden types or, as the focus of this article, taller herbaceous border types. I've been growing Campanula for as long as I can remember. The first was the species most gardeners love to hate; grandmother's-bluebells or Campanula rapunculoides. While this species has an attractive floral display, with one-sided spikes of violet-blue flowers on 60-90 cm stems, they have the terrible habit of producing numerous running rhizomes that infiltrate themselves throughout the garden. The resulting colonies, if left unchecked, can swamp a garden. Such was the case in my own garden where I had the tough job of trying to eliminate this species. The tiniest of rhizomes will quickly regenerate into a new plant. Some 20 years later, I still haven't been successful!
Perhaps the most popular species is the peach-leaved bellflower, C. persicifolia. This bellflower has flowers which are among the largest within the genus. Plants reach 60-90 cm with loose clusters of flowers over a long blooming period, starting in late June and sometimes running through the fall. The flowers are typically blue or white but perhaps the prettiest cultivar is the delicately coloured ‘Chettle Charm' with its white flowers tipped in China blue. Double forms also exist. While easy to grow in sun or shade, plants have rather wiry stems than can be wrecked by windy or wet weather. With their loose habit, staking them can look just as unattractive as the flopped stems. Planting them close to neighbours will provide them with additional support. This species, if not promptly dead-headed, can self-seed all over the garden.
Single and double forms of C. persicifolia along with 'Chettle Charm' (last picture)
Another lovely, if not problematic species, is the spotted bellflower C. punctata. Like C. rapunculoides, this one also runs although it is slightly more easily controlled than the former species. It also readily self-seeds so be prompt in its dead-heading. It is perhaps best grown as a ground-cover. Plants produce 30-60 cm stems with a loose panicle of quite large, tubular-like bells. The wild species has creamy-white flowers with dense pink spotting on the inside. There is also a pure whote form called 'Alba'. More popular is the cultivar 'Cherry Bells' whose flowers are reddish-pink both inside and out. A recent release is 'Plum Wine' whose shiny foliage is tinted purplish, contrasting beautifully with the light mauve-pink flowers. The Korean bellflower C. takesimana ‘Elizabeth', appears quite similar to C. punctata with reddish-pink flowers but is not nearly as rambunctious! These species are one of the parents in the more behaved, very desirable bellflower hybrids 'Burghaltii', 'Kent Belle', 'Sarastro' and 'Van Houttei'. These hybrids have the general habit and flower shapes of C. punctata and C. takesimana but are not invasive and their flowers are shades of blue.
Variation among C. punctata ('Cherry Bells', 'Alba' and 'Pink Chimes')
Campanula hybrids 'Kent Belle', 'Sarastro' and 'Van Houttei'
Another popular garden bellflower is the clustered bellflower, C. glomerata. It is a clump-forming species which also runs to a degree. I would consider it a garden brute rather than being invasive. The stiff stems arise 20-70 cm and end in a rounded dense, terminal cluster. Smaller flower clusters are formed in the upper leaf axils as well. The main flowering season is June-July but prompt deadheading will provide a late summer repeat performance. Among the standard cultivars are 'Crown of Snow' (white), 'Caroline' (pink) and 'Superba' (violet-purple), but dwarf forms, referred to as 'Acaulis' are available with white, blue or violet flowers on stocky 20-30 cm stems.
Variation among C. glomerata ('Crown of Snow', 'Superba' and 'Caroline)
There are two giant, ‘back-of-the-border' bellflowers; the milky bellflower, C. lactiflora and the great bellflower, C. latifolia. The former is perhaps my favourite among the larger bellflowers. The plant habit is not unlike garden phlox, so plants grow as a discrete clump. Plant size is quite variable with compact forms around 30-45 cm while the real grand-daddies may reach to 2 m! The taller selections can be spoiled by windy, wet weather but like phlox, easily take to staking. Flowers are mostly upward to outward facing in rounded panicles and are delightfully fragrant, a characteristic rare among bellflowers. Prompt dead-heading can bring about a secondary floral display. This species has very deep rots and resents transplanting once mature. Popular cultivars include 'White Pouffe', 30 cm; ‘Pouffe', mid-blue, 30 cm; ‘Prichard's Variety', dark purple, 1.5 m; and ‘Loddon Anna', light pink, 1.5 m.
Variation among C. lactiflora
The great bellflower, C. latifolia, has huge (relatively-speaking) outward to downward-facing bells. This species is also a clumper with very stout stems potentially reaching to 2 m. Despite its height, staking is rarely required. Plants produce a long spike of white or blue flowers during mid-summer. This plant is an oldie but goodie and has been grown in gardens of my home province of Newfoundland for well over 100 years. It is one of the featured plants in the Heritage Garden of the Memorial University of Newfoundland Botanical Garden (along with the bully-bellflowers, C. rapunculoides and C. persicifolia). A noteworthy selection is 'Brantwood', compact (around 1 m) with deep violet-blue flowers.
Examples of C. latifolia
In the next installment, I will discuss other border type bellflowers, but these are species not so well-known but equally desirable. Stay tuned!
I would like to thank the following people for their pictures: bootandall (C. lactiflora), galanthophile (C. lactiflora), daryl (C. punctata 'Pink Chimes'), echoes (C. latifolia 'Brantwood'), hczone6 (C. punctata 'Cherry Bells'), kniphofia ('Chettle Charm'), saya (white C. glomerata), Tomtom (C. glomerata 'Caroline', 'Sarastrao' and 'Van Houttei'), trilian15 (C. latifolia alba), Weezingreens (C. latifolia) and Xenomorph (blue C. glomerata)
(Editor's Note: This article was originally published on October 31, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)