Hydrangea ampla (Chun) Y.De Smet & Granados

This magnificent species is a moderately vigorous deciduous climber, suitable for growing on large trees, walls and other structures. Bold, glossy green leaves and flattened inflorescences to about 30 cm across, ringed by the long white bracts of sterile flowers, are its finest features. Shade tolerant, it flowers best with warmth and better light levels (Pan-Global Plants 2023). H. ampla belongs to the tight knit and still quite poorly understood Section Schizophragma, and is still better known as Schizophragma integrifolium. In garden terms these plants have a great deal in common; distinguishing them is the challenge. H. ampla is larger in all parts than the better known H. hydrangeoides, and more impressive when at its best.

All species in Section Schizophragma share a climbing habit, deciduous foliage, enlarged fertile flowers with free petals, and a single (rarely 2–3) sepal per sterile flower (H. crassa lacks sterile flowers). H. ampla is the most widespread schizophragma of mainland China; its range does not overlap with the other commonly grown species H. hydrangeoides (Japan plus nearby islands). H. ampla is larger in all its parts than H. hydrangeoides, which also has far more prominently toothed leaves. Neither does it overlap with H. fauriei (Taiwan, leaves tomentose beneath) or H. crassa (Hand.-Mazz.) Y.De Smet & Granados (W. Yunnan, sterile flowers absent, not described here). H. schizomollis (leaves densely tomentose beneath) occurs within the range of H. ampla, quite widely in central China. Two further species are much more local. The central Chinese H. glaucescens, mainly recorded from Guizhou and Sichuan, has leaves glaucous beneath, with prominent tufts of hair in the vein axils. H. corylifolia (Chun) Y.De Smet & Granados from eastern China seems not to be in Western cultivation, although some plants have been misidentified as such (Shaw 2012): it has serrate leaves (Liu & Zhu 2011). Most of these plants have been treated as variants of H. ampla (as Schizophragma integrifolium) at one time or another. Hence, records from Vietnam, Myanmar and Arunachal Pradesh, India (Royal Botanic Gardens, Kew 2023) which are not mentioned in the revision of Liu & Zhu (2011) should be approached with an open mind. Several interesting schizophragmas collected in northern Vietnam by Bleddyn & Sue Wynn-Jones remain unnamed (B. Wynn-Jones pers. comm. 2023).

This plant was first recognized as distinct from H. hydrangeoides by Oliver (1890), through a herbarium specimen collected near the summit of Emei Shan, Sichuan, by the German missionary-botanist Ernst Faber. The story of its name is less simple. Oliver’s article named it Schizophragma integrifolia, a spelling mistake for integrifolium, since depite appearances the name Schizophragma – from Greek schizo- (split) and phragma (a partition), referring to the fruit – is grammatically neuter rather than feminine (Stearn 1983). On transferring the species to Hydrangea, a different specific epithet was required, since Hydrangea integrifolia was already in use for another Asiatic climbing species; so the accepted name is based on a synonym, Schizophragma amplum Chun (from the Latin amplus – large or abundant). It is too easy to fall foul of these twin traps (viz. Lancaster 2023). Numerous varieties have been named within S. integrifolium and their names will still crop up from time to time. None are current (Royal Botanic Gardens, Kew 2023), most having been described subsequently as other species (see also synonyms above).

One still problematic name for a closely allied plant is H. megalocarpa. Originally described from Emei Shan (as was H. ampla), it is said to have a larger capsule (8–12 mm as opposed to 6–8 mm), with leaves more densely pubescent either side of the midvein beneath (Wei & Bartholomew 2001). Accepted in Flora of China (Wei & Bartholomew 2001), the later and apparently rather careful revision of Schizophragma (Liu & Zhu 2011) which shows no evidence of a prejudice towards extreme taxonomic ‘lumping’, sunk it entirely, although the name appears from time to time on newer collections from Sichuan. The Crûg Farm collection FMWJ 13014 (N Vietnam) has also been linked to the name (Crûg Farm Plants 2023). Similarly, Schizophragma choufenianum Chun (no published name in Hydrangea), described from NE Guangxi and said to differ from H. ampla in having a truncate rather than projecting capsule apex (Wei & Bartholomew 2001), is accepted by Flora of China but not at any level by Liu & Zhu (2011). FMWJ 13217 (N Vietnam, 2011) has been tentatively linked to this name (Crûg Farm Plants 2023).

H. ampla came into Western cultivation in the early 1900s, through Ernest Wilson’s collections. Bean (1981) mentions collections for the Veitch nursery, presumably Wilson for Veitch 1065, 1158 and/or 1320, from W Hupei, 1900–1 (Sargent 1913). A later collection for the Arnold Arboretum from Muping, Sichuan (W 1068 of 1908) is more thoroughly documented (Sargent 1913; Arnold Arboretum 2023; Royal Botanic Garden Edinburgh 2023). All Wilson’s specimens were collected from rocks and cliffs rather than trees (Sargent 1913) but this might simply reflect ease of collection. These seem to be the basis of most garden stocks today. Later collections which have been placed here include SICH 1736 (Sichuan 1996 – Royal Botanic Garden Edinburgh 2023) and SAT 88051 from a joint US/Chinese visit to Huangshan, Anhui in 1988 (US National Arboretum 2023). Roy Lancaster’s L 591 (Emei Shan, Sichuan, 1980) has been well distributed in Britain, sometimes labelled ‘Emei Shan’; it flowered particularly well in 2023 following a heat wave the previous summer (Lancaster 2023). Crûg Farm’s BWJ 8150 (N of Boaxing, Sichuan) also seems to belong here (Shaw 2012). Dan Hinkley’s DJHS 8114 (Emei Shan, 2008) has been labelled aff. H. megalocarpa; whatever the status of that name, it is particularly impressive in flower, with inflorescences to 38 cm across (Hinkley 2023). This remains a taxonomically troublesome species in a troublesome group.

In Europe H. ampla is reasonably widely grown in the British Isles, France and the Low Countries; hardiness restricts is use further north or east. In North America it is largely a plant of serious collections on both seaboards (US National Arboretum 2023; University of British Columbia 2023), but not in colder areas.