Physocarpus opulifolius
An up to 10' high bush. The older stems have papery bark that flakes off in sheets. The alternate, roundish, blunt-toothed leaves have 3 lobes and the base is heart-shaped. The small white flowers are in 1 1/2" umbel-like clusters, and both the umbels and individual flowers are long-stalked. There are 5 roundish petals, 5 smaller sepals and many pink anthers. The fruit has 3-5 papery, inflated compartments, at first green, then reddish-purple. Blooms June. Found in wet places, stream banks.