I have several of these perennial flowering plants. It’s called balloon flower because the flower bud puffs up like a tiny balloon before it opens. However, the official name is platycodon grandiflorus and it is native to East Asia. However, it grows quite well here! The flower has beautiful shiny purple-blue petals. (Although the online images of this flower also include a pink version.) One flower blooms at the top of each plant, which grow less than a foot tall. The ones I planted in a pot alongside the hosta seem to be doing better than the ones in my garden, which get more sun. However, in both places they are starting to bloom at this time.
Source for information: Wikipedia