Answer: Your button bush is Cephalanthus occidentalis. It grows best in sunny areas and grows fastest in moist soil near a pond, but often grows in shallow standing water.
Aside from exposure to sunshine (which you didn't mention), I can't imagine why your larger plant is not blooming. Don't fertilize this year. Sometimes too much nitrogen fertilizer can promote the development of lush green growth, at the expense of blooms. Hope it blooms for you next year!
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