The Witch Hazel just started to flower in our yard last week. I'm always amazed at how late in the year this woody plant flowers. We've already had a frost so there are fewer pollinators available to pollinate the flowers.
Pollination occurs in the fall but the flowers are not actually fertilized until the following spring. The seeds mature the following fall and are ejected from the brown capsules. (Welby Smith, Trees and Shrubs of Minnesota)
American Hazelnut (Corylus americana). They are elliptical in shape with soft wavy edges. The leaves turn a nice yellow to rosy color in the fall.
The flowers are fairly inconspicuous because they often open before the leaves have fallen, and hang downwards below the branch from which they're attached. They are four petaled, thin and twisted and a soft yellow in color.
Witch Hazel is used extensively for medicinal purposes. "Medicinal extracts, lotions, and salves are prepared from the leaves, twigs, and bark of witch-hazel. The distillate is used to reduce inflammation, stop bleeding, and check secretions of the mucous membranes." (Vines, Robert A. 1960. Trees, shrubs and woody vines of the Southwest, p. 1104)