Balloon flowers ((Platycodon)) can be propagated by stem cuttings or seeds. 

Stem cuttings 

In spring, take a 4-inch cutting from a soft, growing stem tip.

Remove the lower leaves from the stem. Dip the cut end in rooting hormone.

Plant the cutting in a pot with a sterile potting mix.

Cover the pot with a plastic bag and place in a bright location.

Keep the soil moist but not soggy.

Wait for new leaf growth, which indicates the cutting has rooted.

Transplant the rooted plant to the garden.

Seeds 

Sow seeds in pots under cover in spring. Harden off the seedlings and transplant them to their final location after the risk of frost has passed.

Alternatively, sow seeds directly in late spring.

Propagate from stem cuttings: * In the spring, take 4-inch cuttings from soft, growing stem tips.

Remove the foliage

Gently excavate the Balloon-Flower, maintaining a 12-inch berth from the central clump to safeguard the taproot.

Sow playtcodon seeds in pots under cover in spring – they need light to germinate.

Tips

Balloon flowers have deep taproots and don’t like to be disturbed, so dividing them is not recommended.  Use sterile, sharp tools to prevent infection.  Keep the soil consistently damp but not waterlogged.  Balloon flowers grow best in full sun or partial shade.  In hotter climates, they may need afternoon shade