Corylus

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.

C. americana

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.

C. cornuta