Sow Inside: Germination time: two to four weeks in the light. Temperature: 70°F (21°C). Use peat pots as seedlings are delicate. Start seven or eight weeks in advance. Transplant outdoors towards the end of spring. Spacing 10 to 18 inches (25—45 cm).
Requirements and care: Full sunlight or light shade. Good drainage. Rich soil, moist soil. Regular watering. Occasional light feed. Deadhead to prolong blooming season. Propagate: by taking cuttings in the summer. Plants can also be propagated by dividing in the spring in cooler areas, or the autumn in warmer areas; this is not recommended as Platycodon grandiflorus is a very delicate plant and is slow to recover from any disturbance.
Miscellaneous: Flower buds swell up before opening, hence the common name of Balloon flower. Roots are used in Korean culinary, and also used in traditional Chinese medicine to treat coughs and for anti-inflammatory purposes. One of the seven traditional Japanese autumn flowers.
How to Grow Balloon Flower
The seeds of Balloon flowers (Platycodon) should be sown on the soil surface. This can be done in either spring or summer.
They have a preference for a rich and moist soil. ideally Platycodon likes to grow in sunny or partially shaded areas of the garden. It is important that the location has good drainage.
If starting off indoors, do so about 7 or 8 weeks in advance. It should take seeds about two to four weeks to germinate at 20 degrees Celsius (68°F).
The seedlings should be transplanted with great care into the garden at the end of spring. Space at about 25 cm to 75 cm (10 to 30 inches) apart, depending upon the size of the Platycodon variety.
Caring for Platycodon
It is quite easy to care for Platycodon. They like a moist soil so keep well watered, and dead head the flowers to extend the period in which they bloom.
As they are very delicate plants it may be wise to carefully stake larger varieties.
It is best to propagate plants by taking cuttings in the spring or growing from seeds. Although the plants can be propagated by division, this can often damage the plant.