Carpinus orientalis Mill.

The natural range of Carpinus orientalis corresponds closely with the south-eastern half of that of C. betulus, but is patchier; the presence of C. orientalis as a wild tree in Syria and Lebanon is not confirmed (Plants of the World Online 2022), while in Iran, in the mountains south of the Caspian Sea, it is represented by its larger-leaved subspecies macrocarpa (see below). Hybrids with C. betulus (C. × schuschaensis) are known from the Caucasus; see the entry for C. betulus for a further discussion of possible intermediate forms.

The two species, in their pure state, are easily distinguished and are not closely related (Dong et al. 2022). Carpinus orientalis is one of the hornbeams with untoothed, ‘D-shaped’ fruit-bracts, and it is a smaller plant than C. betulus in foliage features, with particularly short and finely-toothed leaves. It is often described as a species of smaller stature, and can be a low bush in harsh and open conditions, but in woodland shelter it can become a substantial tree; a 1908 accession in the hornbeam collection at the Royal Botanic Gardens, Kew, is 20 m × 64 cm dbh (Tree Register 2022).

Carpinus orientalis was first introduced to the UK in 1735 for Philip Miller, the long-serving head gardener of the Chelsea Physic Garden (Bean 1976), but has never become a common garden tree, receiving a rather brusque dismissal from Bean himself: ‘It has not much to commend it to the notice of planters in this country except as being an interesting rarity’ (Bean 1976). Although it lacks showy flowers or fruit and its autumn colour is seldom bright, even in the continental climate of the Eastern United States (Dirr 2009), the small leaves mean that it is at least as graceful a tree as the genuinely ‘oriental’ hornbeams which have recently become fashionable collectors’ plants in the UK. (C. orientalis was named, of course, before any of the east Asian taxa were known to western botanists). It is also perhaps the most drought-tolerant Carpinus, a feature seldom shown by its Chinese rivals. Conversely, it is sufficiently tolerant of cool, Atlantic conditions to have grown to 8 m at the Linn Botanic Gardens in Argyll (Tree Register 2022). But in an exception to the fortunes of the genus as a whole, it was still perhaps offered in the UK in 2020 by just one single nursery, Mallet Court (Royal Horticultural Society 2020).

After a very mild winter, a tree planted by David Clulow in his old garden, Tilgates in Surrey, bore one evergreen branch in April 2016 (Tree Register 2022). Another oddity is the collection Cobham 226, which at Kew and at White House Farm in Kent produces a dense grove of vigorous, vertical stems from a much-tangled base (Tree Register 2022), and takes up a considerable amount of space.