Hydrangea pottingeri Maxim.

This is the plant still widely known as Hydrangea chinensis (see taxonomic note above). A widespread member of the baffling H. scandens/pottingeri species complex, it is a relative newcomer to Western gardens, with rather less to commend it than H. angustipetala, H. luteovenosa or H. scandens itself. Hydrangea pottingeri is an upright, early flowering, deciduous shrub, with rather thick, leathery leaves and normally white sterile and yellowish fertile flowers. It can be quite a tall plant. In gardens, younger shrubs may be very attractive, but with age they often become gaunt and leggy, most flowers carried above eye level. It suits light shade in the garden but is too tender for colder parts of our area. It is important to note that anything described as H. pottingeri / chinensis might well belong in H. angustipetala (if one believes in that taxon!), or potentially any other member of the complex.

Hydrangea pottingeri is primarily a mainland species, ranging from the far northeast of India to southeastern China. Flora of China (Wei & Bartholomew 2001) suggests a disjunct distribution, with it absent from south-central and southwestern China. While the bulk of Chinese herbarium specimens are from the southeast, especially Zhejiang and Anhui, contemporary Chinese botanists seem happy to identify it in Guizhou, Sichuan and Yunnan, plugging the gap (Chinese Academy of Sciences 2024). Taiwanese botanists tend to accept both this species (as H. chinensis) and the arguably distinct H. angustipetala on the island, Taiwanese “H. chinensis” having thicker leaves than H. angustipetala, and essentially glabrous branchlets and leaves, as well as a more southerly distribution (Li 1963). The evergreen, more tender, lowland H. lobbii is a third Taiwanese taxon. While some mainland herbarium specimens have in the past been identified as H. angustipetala, these tend now to be labelled H. chinensis (i.e. H. pottingeri) (Chinese Academy of Sciences 2024; Wei & Bartholomew 2001). Japanese H. scandens s.s., H. luteovenosa and H. liukiuensis are all lower growing shrubs with smaller inflorescences and smaller, thinner leaves. The unstalked inflorescences of H. pottingeri are normally only at the ends of shoots rather than on short side shoots along their length, as often seen in the Japanese plants. Some further local segregates are sometimes recognized in mainland China, notably H. linkweiensis Chun (inflorescence stalked, with 3–5 cm peduncle; E Guangxi, SW Hubei) and H. mangshanensis C.F.Wei (bark of second-year branchlets grey-white, not peeling, petals slightly smaller; SE Hunan, N Guangdong) (Wei & Bartholomew 2001; Wei 1994). Probably neither is in cultivation.

H. davidii (recognized from Guizhou, Sichuan, Yunnan, Myanmar & Vietnam) is a troublesome taxon. It appears to belong here morphologically, with even one of the Flora of China authors preferring to treat it as part of the variation of H. chinensis (i.e. H. pottingeri) but some molecular studies group it with quite distantly related hydrangeas (e.g. He et al. 2020; Yang et al. 2024), and Western enthusiasts sometimes point to a plant as ‘what so-and-so calls davidii’. Everyone seems to agree, though, that if it exists as a distinct entity, the fertile flowers have blue rather than yellowish petals. All this variation within the complex was swept into a broadly drawn H. scandens by McClintock (1957), a treatment largely ignored in Asia and only patchily adopted elsewhere. Weakly delineated species and competing taxonomic schemes have led to utterly confusing naming in gardens, an old hydrangea story writ large.

Genus-wide molecular studies have if anything increased the level of uncertainty. De Smet et al. (2015) resolved the complex as monophyletic, sister to H. macrophylla plus H. serrata, allowing them to establish Sections Chinenses and Macrophyllae. However, with wider sampling Yang et al. (2024) found that the H. scandens complex was polyphyletic, H. lobbii and the various Japanese taxa forming a separate clade to H. pottingeri, and leading them to propose a new Section Kawagoeanae for these.

Early 20th century records (of H. chinensis) in Western gardens might not refer to it in this narrow sense. For example Bean (1981) notes that H. scandens subsp. chinensis ‘was at one time in cultivation from seeds sent by Wilson from W. China in 1908 and grown under the name H. davidii’. More definite introductions from the late 20th century are mainly due to Crûg Farm and Dan Hinkley. These include BSWJ 1488, 3271, 3401, 3420, 7055a and 7058, and DJHT 7041 from Taiwan; DJHAP 18023 from Arunachal Pradesh; and BWJ 8000 from Longzhoushan, Sichuan (Crûg Farm Plants 2024; Hinkley 2024).

This remains an experimental garden plant, with much to learn about the hardiness of different introductions.