Platycodon: planting, cultivation, maintenance

Description and Botany

The Platycodon, also known as “Japanese Campanula” or “large-flowered campanula,” is a perennial plant from the Campanulaceae family, native to the grassy slopes and alpine meadows of the Far East, ranging from China to Siberia, including Japan and Korea.

The Platycodon grandiflorus or “large-flowered platycodon” is the only species in the genus. Its original blue-violet flowers are available in several cultivars with pink or white flowers and series, such as the ‘Fuji’ or ‘Astra’ series, which offer dwarf and compact forms.

The Platycodon develops a thick, fibrous, almost tuberous root that produces a round, upright clump with a spreading habit, reaching 10 to 60 cm in height and about 30 cm in spread. A bit slow to establish, the Platycodon needs about two years to fully develop and become floriferous. This slow growth is matched only by its beautiful longevity: once well-rooted, this perennial grows over the years, forming dense, bushy clumps or carpets of flowers.

The plant develops a regular clump of thin, leafy stems that are minimally branched, bearing small deciduous leaves 3 to 5 cm long. Simple, ovate, lanceolate, with irregularly dentate edges, they are whorled at the base of the stems and alternate towards the top. Edible, its young spring shoots can be enjoyed in a crunchy salad. With a beautiful green to bluish-green matte finish, often glaucous on the underside and sometimes edged in red, they take on reddish hues in autumn before disappearing.

The flowering, of infinite delicacy and remarkably generous, stands out against this beautiful grey-tinted foliage that seems to disappear under an avalanche of pastel-hued flowers. It spans the entire summer. At the tips of these erect stems and in the axils of the leaves, from June to September, depending on the climate, curious globose floral buds appear, resembling small green balloons, which has earned the plant the English nickname “balloon flower” or “fleur ballon.”

These large buds, resembling balls, burst into large star-shaped flowers with 5 pointed petals. Some cultivars feature double or semi-double flowers. These well-defined narrow bell-shaped flowers, 3 to 7 cm in diameter, resemble those of its cousin, the campanula.

Platycodon in bud and bloom

The acidic green or pinkish-yellow of the buds transforms upon blooming into a unique blue tinged with lavender or violet, sometimes pure white or pale pink, depending on the cultivars. With a pearly texture, the delicately veined petals reveal fine veins of a more intense hue through the corolla.

These large flowers are also edible and very beautiful in wildflower bouquets.

This endless flowering attracts a large number of pollinating insects. It is followed by the appearance of fruits in autumn, swollen capsules containing numerous small black seeds.

Hardy down to -30°C, heat-resistant and easy to grow, the Platycodon thrives in non-burning sun or partial shade in warm regions, in any good garden soil, fresh, preferably rich and well-drained.

It is used in borders, rockeries, along pathways, and even in a large pot on the terrace or balcony.

In Japan, the flower of Platycodon is often represented in a stylised form in decoration. In traditional Chinese, Japanese, and Korean medicine, the root of platycodon is attributed with anti-inflammatory medicinal properties.

Main species and varieties

The Platycodon grandiflorus is the only species in the genus. It comes in several cultivars with pink or white flowers and is now offered in series such as ‘Fuji’ or ‘Astra’. The latter series features dwarf and compact forms that do not exceed 30 cm in height.

Most Popular

Platycodon grandiflorus Mariesii

It produces abundant intense blue flowers throughout the summer. It forms robust, bushy clumps at the edge of borders or in the background.

• Flowering time August, September
• Height at maturity 40 cm

See the full description

Our Favourites

Platycodon grandiflorus Fuji White

A variety with large bell-shaped flowers, pure white. Ideal for planting at the edge or in the background of borders.

• Flowering time August, September
• Height at maturity 50 cm

See the full description

Platycodon grandiflorus Perimutterschale

Its balloon-shaped flower buds open into large star-shaped flowers of pale, iridescent pink. Plant it at the edge of borders or pathways. It also grows very well in a pot.

• Flowering time July to October
• Height at maturity 25 cm

See the full description

Planting

Where to Plant Platycodon

Very hardy, the Platycodon withstands cold (sometimes down to -35°C) as well as high heat, making it a flower very easy to grow throughout France. It thrives in non-burning sunlight, with a preference for light shade in the hottest regions.

Accommodating, it tolerates all types of soil, even calcareous, but will flourish in good garden soil that is rich, deep, well-drained, light, and cool that does not dry out: it will cope perfectly with summer drought as long as the soil remains cool. While it withstands occasional drought well, it is sensitive to wet winters: waterlogged, compact, clayey soil would compromise its longevity.

Think carefully about its location as its tuberous root can take time to establish and will dislike being transplanted.

It integrates beautifully into natural gardens, in neat borders or as a backdrop in a large romantic perennial bed. It tolerates some shade, making it worthy of a spot in a semi-shaded flowerbed or in the more sheltered areas of a woodland garden. Plant it en masse in pathway borders. Reserve dwarf varieties for large summer pots and cool rockeries.

Platycodon in situ (photo cultivar413-Flickr)

When to Plant Platycodon

It is best planted in spring from February to April in cold climates or in autumn from September to November in mild climates.

How to Plant Platycodon

In Open Ground

The Platycodon grandiflorus prefers soils that remain cool during summer and are well-drained. Add a good amount of well-matured compost if the soil is poor. In very clayey soil, add compost or at least 1/3 gravel to lighten and properly drain the soil. If your soil retains too much moisture, plant it on top of a mound or on a raised bank.

Plan for 5 to 8 plants per m² and maintain a planting distance of 20 to 40 cm between each plant.

• Dig a hole 2 to 3 times the volume of the pot
• Loosen the soil deeply, removing stones and weeds
• Add well-draining gravel to the bottom of the hole
• Add a good handful of mature compost to the soil
• Position the root ball
• Backfill the hole, ensuring the collar is level with the soil
• Water regularly to ensure good establishment in the first few days after planting, then less frequently
• Apply mulch to retain soil moisture

Planting Platycodon in Pots

Plant the Platycodon in a deep pot with a minimum diameter of 30 cm to allow its fleshy roots to develop comfortably. Although Platycodon is well-suited to pot cultivation, it is not an indoor plant; keep it outside in winter, as it is very hardy and does not fear the cold!

• Spread a good layer of draining gravel or clay balls at the bottom of the pot
• Plant in a slightly sandy mix of potting soil for geraniums or flowering plants
• Water
• Mulch the base

For more information, see: How to Grow Platycodon in a Pot?

Maintenance and Care

Less demanding, the Platycodon requires very little maintenance, thriving in dry conditions in cool soil as well as enduring harsh winters.

Mulch the soil in late May to keep it cool throughout the summer and water regularly during dry spells.

Somewhat greedy, the Platycodon prefers fertile soils: it will appreciate a little compost or manure applied by superficial scratching at its base each year at the end of winter.

Regularly remove faded flowers to extend the flowering period.

The Platycodon completely disappears in winter; be sure to mark its location in autumn to avoid accidentally uprooting it during weeding!

In autumn, using pruning shears, cut back all flower stems by trimming the clumps down to ground level. Allow them to seed if you wish to reserve them for sowing.

In pots, the Platycodon needs plenty of water: never let the compost dry out. To support its flowering, apply fertiliser for flowering plants once a week.

Diseases and potential pests

The Platycodon is a disease-resistant perennial. Slugs and snails can attack the young shoots when they appear in spring. And as it completely disappears in winter, starting very late in spring, not before April-May, it is recommended to mark its location in autumn to keep gastropods away when growth begins. Discover our tips for combating slugs!

Propagation of Platycodon

The Platycodon is easily propagated by sowing. Division of clumps in spring is also possible, although more delicate, as once established, the plant does not like to be disturbed.

By sowing

You can harvest seeds from the year at the end of summer and sow them in spring.

• In April, sow Platycodon seeds indoors in trays or individual pots (1 to 2 seeds) in a mixture of compost and turf
• Lightly cover the seeds with compost
• Firm down and keep the soil moist until germination, which occurs in three to six weeks
• Place your seedlings out of direct sunlight
• Transplant the seedlings in autumn into pots
• Install your young plants in the garden or in larger pots the following spring

Sowing in open ground

• In well-prepared soil enriched with compost, sow sparsely directly in place and out of direct sunlight
• Cover them with a thin layer of compost without burying them deeply
• Firm down and water until germination (2 to 3 weeks), keeping the soil moist
• Thin out after germination, keeping one plant every 30 to 40 cm
• Protect from slugs

Division

Divide the most mature clumps and only resort to this risky operation if the plant shows signs of fatigue, as Platycodon roots do not like to be disturbed.

• Using a fork, gently lift the clump, as the roots are fragile
• Separate a few clumps containing roots
• Replant immediately in the garden in well-prepared soil

Associate

The flowers of the Platycodon will bloom abundantly from late spring to early autumn, surrounded by other easy-going summer-flowering perennials. It is useful for adding colour to gardens in summer, during the flowering lull, and is essential in the scenes of a romantic garden.

At the edge of a flowerbed, it will bring a delicate and neat touch alongside roses, poppies, paniculate phlox, ornamental garlic, foxgloves, aconites, or gypsophilas. In a rockery, surround it with other low-growing plants such as campanulas and clumps of Dianthus.

An example of association: Rose ‘Ballerina’, Rose ‘Scepter’d Isle’, Thalictrum actaefolium ‘Perfume Star’, Selinum wallichianum, Geranium ‘Johnson’s Blue’, Platycodon grandiflorus ‘Perlmutterschale’

Its flowers in pastel shades will reign in a pink garden or a white garden, unable to compete with bright and garish colours, but they create a lovely effect with plants featuring purple or variegated white foliage such as heucheras and bugle. It will look stunning enhanced in an environment of green, silver, or glaucous foliage from ferns, hostas, hardy geraniums, and Echinops. It offers a beautiful contrast with the green-yellow flowers and leaves of alchemilla and the grasses of Chinese fountain grass.