It is the rare garden plant that is the sole representative within its genus, but the balloon flower or Chinese bellflower, Platycodon (Campanulaceae) is one such plant. The genus Platycodon is composed of a single species, P. grandiflorus. The genus name comes from the Greek platys meaning ‘broad' and codon meaning ‘bell'. ‘Broad bell' certainly is a apt description of the flower shape. This hardy perennial (suitable for as cold as zone 3) is a native of China, Manchuria and Japan. Plants are variable in size depending on the cultivar, but the tallest are generally under 75 cm or 2.5 feet. Plants arise from a tap-root. The leaves have a dull finish and often a bluish tint. The open clusters of flowers are produced at the ends of the upright stems. Before opening, the flower buds are quite inflated and indeed look like blue balloons. These open to wide, bell-shaped flowers that may be 5 cm or more in diameter. They bloom from mid to late summer, even into autumn in cooler climates. They make admirable cut-flowers.
In the garden, they are useful for the mid-border or even rock garden settings. They prefer a deep, well-drained soil but are not fussy about soil pH. Full sun is best but they will tolerate dappled shade in warm climates. There are two important factors to keep in mind when growing balloon flowers. First, they are relatively late to emerge in the spring so carefully mark the planting site so you do not accidentally dig them up in spring thinking you have a gap that needs filling (I've done that myself!). Secondly, their deeply-delving roots resent transplanting so start with a young plant and once planted, do not disturb them. Like a fine wine, they improve with age. Propagation is quite easy from seed with plants blooming in their second season.
Balloon flowers have been cultivated in China and Japan for hundreds of years. Not surprisingly, a plant with such a long gardening history has plenty of named cultivars. In fact, there are well over 40 cultivars of balloon flowers. These vary in plant size (from 15 to 75 cm) and flower colour, which includes every shade of blue as well as white, pink and splash-pettaled. There are even double-flowered forms. I won't go into every one of these but a few of the more standrad cultivars are worthy of mention.
Some of the oldies but goodies include ‘Mariesii' (60-75 cm, blue), the ‘Apoyama' series (20 to 25 cm), ‘Shell Pink' (20 to 30 cm), ‘Mother of Pearl' (60 cm, light pink) and ‘Komachi' (45 to 60 cm, blue). More recently has come the Fuji series which include single-flowered blue, pink or white flowers. These plants are more compact and bushy than some of the older varieties, reaching 40 to 50 cm (15 to 20 inches). Some newer dwarfs include ‘Sentimental Blue' (20 to 30 cm) and ‘Miss Tilly' (super dwarf blue at just 15 cm). Among the taller double-flowered cultivars are ‘Hakone Blue' and ‘Hakone White'. Both reach 60 to 75 cm. Most unusual are the cultivars ‘Florovariegatus' and ‘Axminster Streaked' which have white flowers variously spotted and streaked with violet-blue.
Part of the 'Fuji' series are 'Fuji Blue', 'Fuji White' and 'Fuji Pink'
Other cultivars include 'Hakone Blue', 'Hakone White' (above), 'Flrovariegatus' and 'Mother of Pearl' (below)
The most recent introduction is the wonderful Astra series. These compact (25 cm) selections are extremely bushy and floriferous, appearing more like a Carpathian harebell (Campanula carpatica) than the standard balloon flower. The Astra series include ‘Astra Blue', ‘Astra Pink', ‘Astra White', ‘Astra White Double', ‘Astra Lavender Double' and ‘Astra Blue Double'. These are popular as pot flowers for patios as well as for garden settings.
Pictures above are some of the Astra series: 'Astra Pink', 'Astra Blue' and 'Astra White'
There are no doubt other cultivars. Any and all are wonderful, carefree plants with few disease or pest problems. If you don't grow this wonderful plant, I highly recommend you track down a balloon flower for your garden; you won't be disappointed.
I would like to thnak the following people for the use of their pictures: buddeyallen ('Fuji Pink'), Equilibrium ('Astra White'), Fro_Bro26 (clump of balloon flowers), joesinay ('Astra Blue'), LilyLover_UT ('Hakone Blue' and 'Hakone White"), onewish1 ('Mother of Pearl'), Evert ('Fuji Blue'), staceysmom ('Astra Pink') and Ursula ('Florovariegatus')