The European filbert is Corylus avellana L., and the fruits of our species also provide edible nuts.
1. Plants with scattered dark stiff gland-tipped bristles as well as very fine ± crinkly whitish hairs on petioles and young branchlets (and often upper leaf surfaces and involucral bracts); staminate aments on short woody peduncles or branchlets; involucre a pair of separate, broadly fan-shaped, sharply lacerate-toothed bractlets, scarcely twice as long as mature nut, which is often partly visible.
1. Plants without dark or gland-tipped bristles (although some whitish hairs, especially copious on involucre, are longer, stiffer, and straighter than in C. americana); staminate aments sessile or nearly so; involucre a tubular prolongation of united bractlets, toothed at apex, ca. 2–5 times as long as the completely concealed nut.
All species found in Corylus
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. June 24, 2018. https://www.michiganflora.net/genus.aspx?id=Corylus.