Platycodon: planting, cultivation, care

Description and botany

The Platycodon, also called “Japanese bellflower” or “large-flowered bellflower”, is a perennial plant of the family Campanulaceae, native to grassy slopes and upland meadows of the Far East from China to Siberia, via Japan and Korea.

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

Platycodon develops from a thick fibrous, almost tuberous root into a rounded, upright tuft with a spreading habit, reaching 10 to 60 cm in height and about 30 cm spread. A little slow to establish, Platycodon needs around two years to bulk up and become fully floriferous. A slow growth that matches a fine longevity: once well rooted, this perennial grows over the years to form dense, bushy clumps or flowering mats.

The plant produces a regular clump of slender, sparsely ramified leafy stems bearing small deciduous leaves 3 to 5 cm long. Simple, ovate to lanceolate, with irregularly dentate margins, they are whorled at the base of the stems and alternate towards the stem tips. Edible, its young spring shoots are enjoyed raw in crisp salads. A pleasing green to bluish-matte green, often glaucous beneath, sometimes marginate with red, leaves take reddish hues in autumn before dying back.

Flowering of infinite delicacy and remarkable generosity stands out against this attractive grey-tinged foliage that seems to disappear beneath an avalanche of pastel-hued flowers. It lasts through summer. At the tips of the erect stems and in the axils of the leaves, from June to September, depending on climate, appear curious globose floral buds shaped like small green balloons, which earned the plant the English nickname “balloon flower” or “balloon flower”.

These large ball-like buds burst into large star-shaped cup flowers with five pointed petals. Some cultivars produce double or semi-double flowers. These well-defined narrow bell-shaped flowers, 3 to 7 cm across, recall those of its bellflower cousin.

Platycodon in bud and in flower

The acidic green or pinkish-yellow of the buds changes on opening to a unique blue tinged with lavender or violet, sometimes pure white or pale pink, depending on cultivar. With a pearly texture, the delicately veined petals reveal fine vessels of a deeper shade through the corolla.

These large flowers are also edible and very handsome in rustic bouquets.

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

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

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

In Japan, the flower of Platycodon is often represented in 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

Le Platycodon grandiflorus est la only species of the genus. It declinates into a few cultivars with pink or white flowers and is now offered in seriates such as ‘Fuji’ or ‘Astra’. The latter series offers dwarf and compact forms not exceeding 30 cm in height.

Most popular

Platycodon grandiflorus Mariesii

Produces abundant deep blue flowers all summer. Forms robust, bushy clumps for bed edges or mid-border.

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

See the full description

Our favourites

Platycodon grandiflorus Fuji White

Variety with large, bell-shaped, pure white flowers. Plant in border or mid-border positions.

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

See the full description

Platycodon grandiflorus Perimutterschale

Balloon-shaped buds open into large, star-shaped flowers of pale, pearly pink. Plant in bed edges or along paths. 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, Platycodon resists cold (sometimes down to -35°C) as well as high heat, making it a very easy-to-grow flower throughout France. It grows in sun that is not scorching, with a preference for light shade in the warmest regions.

Accommodating, it tolerates all types of soil including calcareous, but will thrive in good garden soil that is rich, deep, well-drained, light and cool and does not dry out: it will withstand summer drought provided the soil remains cool. While it copes well with short dry spells, it is, however, vulnerable to wet winters: waterlogged, compact clay soil will shorten its longevity.

Think carefully about its location because its tuberous root sometimes takes time to establish and will hate transplanting.

It fits perfectly into naturalistic gardens, in a neat border or as a mid- or background plant in a large romantic perennial bed. It tolerates shade enough to deserve a place in a semi-shaded border or in the more sheltered parts of a wooded garden. Plant it en masse along paths. Reserve dwarf varieties for large summer containers 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 that are well drained. Add plenty of well-rotted compost if soil is poor. In very clayey soil, add compost or at least one third gravel to lighten it and improve drainage. If your soil retains too much moisture, plant on top of a mound or raised bank.

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

• Dig a hole 2 to 3 times the volume of the bucket
• Fork the soil deeply, remove stones and weeds
• Add well-draining gravel to the bottom of the hole
• Add a good shovelful of well-rotted compost to the soil
• Position the rootball
• Refill the hole, collar at soil level
• Water regularly to ensure good establishment in the first days after planting, then reduce watering
• Apply a mulch to preserve soil coolness

Planting Platycodon in a pot

Plant Platycodon in a deep pot of at least 30 cm diameter to allow its fleshy roots to develop comfortably. Although Platycodon adapts well to container culture, it is not a houseplant — keep it outdoors in winter, as it is very hardy and not afraid of the cold!

• Spread a good draining layer of grit or clay pebbles in the base of the pot
• Plant in a slightly sandy mix of potting compost for pelargoniums or flowering plants
• Water
• Mulch the crown

More information in : How to grow Platycodon in a pot?

Care and maintenance

Undemanding, the Platycodon requires very little maintenance, tolerating drought in cool soil as well as harsh winters.

Mulch soil in late May so it stays cool throughout summer and water regularly during dry spells.

Rather demanding, Platycodon prefers fertile soil: it will appreciate that you work in lightly at its base, a little compost or manure each year at the end of winter.

Remove faded flowers regularly to prolong flowering.

Platycodon disappears completely in winter; remember to mark its position well in autumn to avoid accidentally pulling it up during weeding!

In autumn, with pruning shear, prune all flower stems by cutting clumps back to soil level. Leave to set seed if you want to save seeds for sowing.

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

Potential diseases and pests

Platycodon is a disease-resistant perennial. Snails and slugs can attack young shoots when they emerge in spring. As it dies back completely in winter and starts very late in spring, not before April–May, it is recommended to mark its location in autumn so gastropods can be kept away when the growing season begins. Discover our tips for controlling slugs!

Propagating Platycodon

Platycodon multiplies easily by sowing. Division of clumps in spring is also possible, although more delicate, because once in place plant does not like to be disturbed.

By sowing

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

• In April sow platycodon seeds under cover in a seed tray or in individual bucket (1 to 2 seeds) in a mixture of potting compost and turf
• Cover seeds lightly with potting compost
• Firm down and keep compost moist until emergence, which occurs in three to six weeks
• Keep your sowings sheltered from direct sun
• Prick out seedlings in autumn into buckets
• Plant young plants in garden or into larger pots the following spring

Direct sowing in open ground

• In well-worked soil enriched with potting compost, sow thinly directly in place and sheltered from direct sun
• Cover with a thin layer of potting compost without burying deeply
• Firm and water until emergence (2 to 3 weeks), keeping soil moist
• Thin after emergence, keeping only one young plant every 30 to 40 cm
• Protect from slugs

Division

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

• Using a fork or spade, lift the clump gently, roots are fragile
• Separate a few clump divisions that include roots
• Replant immediately in garden in well-worked soil

Associate

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

In the border it will add a delicate, neat touch alongside roses, poppies, paniculate phlox, ornamental alliums, foxgloves, aconites or gypsophilas. In a rockery, surround it with other small low-growing plants such as campanulas and clumps of dwarf Dianthus.

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

Flowers of pastel‑toned cultivars will reign in a pink garden or a white garden; they cannot compete with bright, gaudy colours but look very attractive with plants bearing purplish or variegated with white foliage such as heucheras and bugles. They are particularly lovely set against green, silver or glaucous foliage of ferns, hostas, hardy geraniums and Echinops. They provide a fine contrast with green‑yellow flowers and leaves of alchemillas and grasses such as Pennisetum.