<em>Platycodon</em>: planting, cultivation and care

Description and botany

Platycodon, also called “Japanese bellflower” or “large-flowered bellflower”, is a perennial plant of family Campanulaceae, native to grassy slopes and high-altitude prairies 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 blue-violet flowers are originally blue but are available in some cultivars in pink or white and in series, such as ‘Fuji’ or ‘Astra’, which offer dwarf, compact forms.

Platycodon develops from a thick fibrous, almost tuberous root into a rounded, erect clump with a spreading habit, reaching 10 to 60 cm in height and about 30 cm in spread. A little slow to establish, Platycodon needs about two years to bulk up and become truly floriferous. Slow growth is matched by great longevity: once well rooted, this perennial grows year after year to form dense, bushy clumps or flowering carpets.

Plant forms a regular clump of thin, leafy, sparsely ramified stems bearing small deciduous leaves 3–5 cm long. Simple, ovate to lanceolate, with irregularly dentate margins, leaves are whorled at base of stems and alternate towards stem tips. Edible, its young spring shoots can be eaten in a crunchy salad. A handsome matte green to bluish-green, often glaucous beneath, sometimes marginate with red, leaves turn reddish in autumn before disappearing.

Flowering is infinitely delicate and remarkably generous, standing out against this attractive grey-tinged foliage that seems to disappear beneath an avalanche of pastel-coloured flowers. Flowering is spread throughout summer. At tips of these erect stems and in leaf axils, from June to September, depending on climate, appear curious globose flower buds shaped like small green balloons, which gave plant its English nickname “balloon flower” or “balloon”.

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

Platycodon in bud and in flower

Bud colour, acid green or pinkish-yellow, becomes at opening a unique blue tinged with lavender or violet, sometimes pure white or pale pink, depending on cultivar. With a nacreous texture, the delicately veined petals show fine veins of a deeper shade through the corolla.

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

This seemingly endless flowering attracts many pollinators. It is followed in autumn by inflated capsules containing numerous small black seeds.

Hardy down 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, rather rich and well-drained.

Use in borders, rockeries, along paths and even in a large pot on terrace or balcony.

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

Main species and varieties

Platycodon grandiflorus is the only species of the genus. It is available in a few cultivars with pink or white flowers and is now offered in series 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 product sheet

Our favourites

Platycodon grandiflorus Fuji White

A variety with large bell-shaped flowers, pure white. Plant at bed edge or mid-border.

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

See the product sheet

Platycodon grandiflorus Perimutterschale

Its flower buds shaped like balloons open into large star-shaped flowers of pale, pearly pink. Plant at bed or path edge. Also grows very well in a pot.

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

See the product sheet

Planting

Where to plant Platycodon

Very hardy, Platycodon resists cold (sometimes down to -35°C) as well as high heat, making it a flower very easy to grow throughout France. It grows in non-scorching sun, with a preference for light shade in the warmest regions.

Accommodating, it tolerates any soil type, even calcareous, but will thrive in good garden soil that is rich, deep, well-drained, light and cool and does not dry out: it will tolerate summer drought provided soil remains cool. While it copes well with temporary drought, it dislikes wet winters: waterlogged, heavy clay soil would shorten its lifespan.

Think carefully about 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/second layer in a large romantic perennial bed. It tolerates shade enough to deserve a place in a semi-shaded border or in the more shaded parts of a woodland garden. Plant it en masse along path edges. Reserve dwarf varieties for large summer containers and cool rockeries.

Platycodon in its setting (photo cultivar413-Flickr)

When to plant Platycodon

Preferably 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 plenty of well-rotted compost if soil is poor. In heavy clay soil, add compost or at least one third gravel to lighten it and improve drainage. If soil holds too much moisture, plant on top of a mound or on a raised bank.

Allow 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 bucket
• Fork soil deeply, remove stones and weeds
• Add well-draining gravel to bottom of hole
• Add a good shovelful of well-rotted compost to soil
• Set rootball in place
• Backfill hole, collar at soil level
• Water regularly to ensure good establishment in first days after planting, then reduce
• Apply mulch to keep soil cool

Planting Platycodon in pots

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

• Spread a good draining layer of grit or clay balls in bottom of pot
• Plant in a slightly sandy mix of potting compost for geraniums or flowering plants
• Water
• Mulch base of plant

Care and maintenance

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

Mulch the soil in late May so it stays cool all summer and water regularly in dry periods.

Rather greedy, Platycodon prefers fertile soils: it will appreciate a little compost or manure worked in superficially at its base each year in late winter.

Remove faded flowers regularly to prolong flowering.

Platycodon dies back completely in winter; remember to mark its location well in autumn to avoid pulling it up accidentally during weeding!

In autumn, using pruning shear, prune all flower stems, cutting clumps back to ground level. Leave them to set seed if you want to save them for sowing.

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

Diseases and potential pests

Platycodon is a disease-resistant perennial. Slugs and snails can attack young shoots when they appear in spring. Because it dies back completely in winter, only starting very late in spring, not before April–May, it is recommended to mark its position in autumn so you can keep gastropods away when growth starts. Discover our tips for controlling slugs!

Propagation of Platycodon

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

By sowing

You can harvest this year’s seeds at end of summer and sow them in spring.

• In April sow Platycodon seeds under cover in a seed tray or in an individual bucket (1 to 2 seeds) in a mix of potting compost and turf
• Cover seeds lightly with potting compost
• Firm down and keep soil cool until germination, which takes three to six weeks
• Keep your sowings out of direct sunlight
• Prick out seedlings into buckets in autumn
• Set out young plants in garden or in larger pots the following spring

Sowing in open ground

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

Division

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

• Using a fork and spade, lift rootball gently, roots are fragile
• Separate a few clump divisions including 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 that are easy to grow. Useful for bringing colour to gardens in summer during the lull in flowering and indispensable in scenes of a romantic garden.

En bordure de massif, il apportera une touche délicate et soignée en compagnie de rosiers, pavots, phlox paniculés, d’ail d’ornement, de digitales, d’aconit ou de gypsophiles. Dans une rocaille, entourez-le d’autres petites plantes basses comme des campanules, des touffes de Dianthus nains.

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

Flowers of cultivars with pastel shades will be regal in a pink garden or a white garden; they cannot compete with bright, garish colours but work very well with plants bearing purple foliage or foliage variegated with white, such as heucheras and bugles. They look particularly handsome 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 Alchemilla and the grasses Pennisetum.