Ostrya

Ostrya is a genus of eight to 10 small deciduous tree species belonging to the birch family, Betulaceae. Common names include hop-hornbeam, hophornbeam and sometimes ironwood, a name shared with a number of other plants.

The genus is native in southern Europe, southwest and eastern Asia, and North and Central America. They have a conical or irregular crown and a scaly, rough bark. They have alternate and double-toothed birch-like leaves 3–10 cm long. The flowers are produced in spring, with male catkins 5–10 cm long and female aments 2–5 cm long. The fruit form in pendulous clusters 3–8 cm long with 6–20 seeds; each seed is a small nut 2–4 mm long, fully enclosed in a bladder-like involucre.