What plant is that?

September’s Mystery Plant is a native multiple-trunked shrub that grows 5-20′ tall along wetland margins. The smooth grayish trunks lack conspicuous lenticels. Younger twigs are light green and pubescent. The alternating obovate or broadly elliptic leaves measure 2-5″ by 1-3″ with finely serrated and slightly wavy margins. The lower leaf surfaces are glabrous to sparsely pubescent, usually along the central vein. Leaf venation is pinnate with 8 or more pairs of straight veins. The fruits are catkins: the males elongating dramatically in the spring and the females persisting in winter, making it easy to ID to genus at least.