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Owen Johnson (2022)
Johnson, O. (2022), 'Carpinus rankanensis' from the website Trees and Shrubs Online (treesandshrubsonline.
Tree to 10 m. Bark dark grey, soon roughened. Twigs brown, glabrous. Leaves oblong to elliptic, 8–10 × 3–4 cm, flushing reddish; base cordate; upper surface glabrous except along the midrib; lower surface with silky hairs along the veins, lateral veins in 20–25 closely parallel pairs; margins irregularly double-serrate, teeth with mucronate tips; petiole glabrous, 0.5–1 cm long; stipules soon falling. Fruting catkin terminal, 10–12 cm long, the peduncle sparsely pubescent. Fruit-bracts ripening whitish, densely overlapping, c. 13 × 7 mm, with 3 veins, both sides remotely serrate or entire and curved over the nutlet; nutlet with very faint ribs. (Li & Skvortsov 1999).
Habitat Mountain forests, 1000–2000 m asl.
USDA Hardiness Zone 7-8
RHS Hardiness Rating H5
Conservation status Least concern (LC)
The only Taiwanese representative of the ‘false hornbeams’ (Section Distegocarpus), Carpinus rankanensis was named from the lost village of Rankan-zan in the island’s mountainous northeast (University of British Columbia 2018), and shares the showy fruit and many neatly parallel leaf-veins of its close allies. It is the rarest in cultivation of these four species, but has been introduced several times since 1992, when Tony Kirkham and the late Mark Flanagan collected seed in a ravine at 1900 m on Taipingshan (ETOT 122) (Grimshaw & Bayton 2009). The example of this collection at Kew was 8 m tall in 2022, while another from BSWJ 3404 had reached seven metres at White House Farm in Kent, and fruits showily and reliably (Tree Register 2022; M. Foster pers. comm.). The Kew tree can retain its leaves until December, before they turn yellow (Grimshaw & Bayton 2009). The species is hardy enough to grow, albeit slowly, at the Royal Botanic Garden Edinburgh, where a plant from ETE 131 (1993) was 4 m tall in 2015 (Tree Register 2022); it also survives at the David C. Lam Asian Garden of the University of British Columbia in Vancouver, Canada (University of British Columbia 2022). At the Grange Farm Arboretum in the Lincolnshire Fens – a situation differing drastically from the free-draining but rain-soaked limestone crags of its native habitat – one of two young trees was struggling in 2019 (Tree Register 2022). The species is commercially available in the UK, where offerings include seedlings from NMWJ 14544 and RWJ 9839 (Crûg Farm Plants 2022).
Flora of China (Li & Skvortsov 1999) and Plants of the World Online (Plants of the World Online 2022) distinguish var. matsudae, from c. 1000 m in the Gaoxiong Shi, whose fruit-bracts are slender and long-pointed and whose nutlets are oblong rather than ovoid. This form is not known to be in cultivation.