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 3âÂÂ10 cm long. The flowers are produced in spring, with male catkins 5âÂÂ10 cm long and female aments 2âÂÂ5 cm long. The fruit form in pendulous clusters 3âÂÂ8 cm long with 6âÂÂ20 seeds; each seed is a small nut 2âÂÂ4 mm long, fully enclosed in a bladder-like involucre.
The wood is very hard and heavy. The genus name Ostrya is derived from the Greek word (), which may be related to () "shell (of an animal)". Regarded as a weed tree by some foresters, this hard and stable wood was historically used to fashion plane soles.
Ostrya species host the larvae of various Lepidoptera species, providing food for winter moth, walnut sphinx, and Coleophora ostryae.
Ostrya has the following species:
â Ostrya scholzii fossil seeds of the Chattian stage, Oligocene, are known from the Oberleichtersbach Formation in the Rhön Mountains, central Germany.