Carpinus laxiflora (Sieb. & Zucc.) Blume

Among the many often marginally distinct oriental taxa with Section Carpinus, C. laxiflora is a fairly recognisable species, differing from the Himalayan and Chinese C. viminea largely in terms of native range – C. viminea does tend to have less markedly double-toothed leaves – and otherwise appearing most closely related to the American taxa C. caroliniana and C. tropicalis, whose fruit-bracts are also asymmetrically three-lobed (Dong et al. 2022). The lax catkins of small green fruit and the rather long stalks – for a hornbeam – to its oval leaves, combined with its general daintiness and the grey bark with its faint, silvery snakes, slightly recall some forms of the snake-bark maple Acer davidii, while the leaves’ long, tail-like points, themselves jaggedly toothed, can resemble the points of the lobes of the leaf of some other maples, such as A. acuminatum.

The Chinese trees once grown in the UK as Carpinus laxiflora var. macrostachya Oliv. are now considered to belong within C. viminea, leaving C. laxiflora itself as a scarce plant largely confined to collections. (A possible anomaly concerns the population in Korea, where Plants of the World Online (Plants of the World Online 2020) suggests that both C. laxiflora and C. viminea are native. The Sea of Japan, and the broad region of northern China where neither species is known to grow, both present plausible barriers to prevent gene flow and to facilitate speciation. The differences between these very closely allied species present a less plausible barrier.) In the UK, Ernest Wilson’s collection W 7745 is represented by a 9 m tree at Borde Hill (Tree Register 2022), but other examples are much younger. In the hornbeam collection at Kew, BECX 160, planted in 1982, is 7 m tall, while a tree from KFBX 87 (1989) has luxuriated and reached 12 m by 2022 (Tree Register 2022). A plant from Miller & Hillier 325 was added to the Sir Harold Hillier Gardens in 1982, while at Sandling Park in Kent an accession from Chollipo Arboretum in 1989 has failed to thrive (Tree Register 2022). These four introductions derive from from the potentially complex South Korean population; collections of Japanese provenance include BSWJ 8772, which has reached three metres at White House Farm in Kent in 2019 (Tree Register 2022), BSWJ 10809, and BSWJ 11035, all offered by Crûg Farm Plants in 2022 (Crûg Farm Plants 2022).

Like many Japanese and Korean plants, Carpinus laxiflora probably prefers a more continental climate with warm summers, and can be very hardy. In the south-eastern United States, autumn colours are bright yellow and red (Dirr 2009), while the species thrives in protected locations in the Ottawa Valley of Canada (Stewart 2010). It is also grown at the Denver Botanic Gardens (Royal Botanic Garden Edinburgh 2022), and there is a particularly good specimen at the United States National Arboretum in Washington DC (Stewart 2010). In continental Europe, it is offered by nurseries in France, the Netherlands, Germany and Poland.

In the southern hemisphere, there is an example at Hackfalls Arboretum in New Zealand (Golik 2017).