A genus of 3 deciduous shrubs, to 5 m tall, suckering from the base. Leaves alternate, short-stalked, toothed, usually irregularly and doubly, often deeply incised. Monoecious; male flower a short nodding catkin enclosed in a bud through winter, terminal or lateral on old wood, with numerous bracts each subtending 1 flower; stamens 4–8. Female flowers clustered terminally on new wood or in axils, lacking petals; styles crimson. Fruit a small ovoid nut in a crowded cluster, each nut enclosed within greenish bracts that form a leathery sheath which is sharply lobed at its apex and splits on one side when the nut is ripe. Flowers May–June, fruits July–August (in China). (Li & Skvortsov 1999; Bean 1976).
The occasionally encountered name ‘hazel-hornbeam’ indicates the position of this little genus near to the root of the subfamily Coryloideae of the Birch Family (Betulaceae): the relationship to the hazels (Corylus) is obvious in the suckering bushy habit and the leaf-shape, while the size of the nut is more like that of the hornbeams (Carpinus), whose male catkins are similarly protected by a bud through winter. Joseph Decaisne’s generic name means ‘looking like an Ostrya’, and introduces the third genus in this subfamily. The long fruit-bracts of Ostryopsis, which are leathery and split on one side when the nut is ripe, is a distinctive feature. The small nuts are said to be a delicacy in China (Wikipedia 2022), and the timber (when big enough) is strong and used for tool handles (Li & Skvortsov 1999).
Three species of Ostryopsis are known, all endemic to China and all similar in appearance. O. davidiana Decne., widespread in the north of the country, maintains a rather tenuous presence in cultivation in the west. O. nobilis Balf.f. & W.W.Sm., the Yunnan Tiger Hazel, has a restricted distribution in south-west Sichuan and north-west Yunnan and is assessed as Vulnerable (IUCN 2016). The first European to see it was George Forrest in 1913 (Bean 1976), but O. nobilis may never have been introduced to Europe or North America; it is in ex-situ cultivation in China (Beech, Shaw & Jones 2015). A third species, O. intermedia B. Tian & J.Q. Liu, was described in 2010 from Sichuan, having originally been treated as a variety of O. davidiana (Corylus davidiana var. cinerascens Franch.) (Holstein & Weigend 2016). It is a diploid now understood to be of a recent natural hybridization event between O. davidiana and O. nobilis (Liu et al. 2014).