balloon flower

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A perennial plant (Platycodon grandiflorus) native to East Asia, having large balloon-shaped buds and usually blue star-shaped flowers, and cultivated as an ornamental.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A perennial herb, Platycodon grandiflorus, from Asia, having ornamental blue star-shaped flowers.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun fragrant puffed-up white to reddish-pink flowers in long narrow clusters on erect stems; Arizona to New Mexico and Utah