Hydrangea scandens (L.f.) Ser.

This is a small-leaved, early flowering deciduous shrub suiting light shade in the garden. It is part of a mind-boggling species complex (the ‘black hole’ of Hydrangea – Dirr 2021), one of two widespread Japanese members, along with H. luteovenosa. The H. scandens/pottingeri complex as a whole is discussed under H. pottingeri, itself still better known as H. chinensis.

Hydrangea scandens is found widely across western/southern Japan, from south-central Honshu westwards as well as in Shikoku and Kyushu; H. luteovenosa has a broadly similar range. H. scandens is typically a smaller shrub than H. pottingeri, and does not have the same tendency to become tall and leggy over time.The slender shoots are sometimes long and straggly, probably inspiring the specific name, although this is in no way a climbing plant. It has leaves intermediate in size between H. pottingeri and H. luteovenosa (4–7 cm long, versus 5–12 cm in H. pottingeri, ~3 cm in H. luteovenosa), typically glossy dark green above at maturity. As in H. luteovenosa, inflorescences are often borne on short side shoots down the length of the previous year’s growth, as well as at the shoot tips, an ornamental feature. Sterile flowers with only three sepals are absolutely the norm in this species (Wei & Bartholomew 2001; Ohba 2001; Foster 2023).

H. scandens became known to Western science through Carl Thunberg, who was based in Japan during 1775–6 with the Dutch East India Company. It was first described as a Viburnum: Linnaeus’s name Viburnum scandens unfortunately predates Thunberg’s own, more appropriate V. virens by two years (Linnaeus 1782; Thunberg 1784). Neither author recognized Hydrangea luteovenosa, and their descriptions would cover both species. The early date meant that when taxonomic lumper McClintock (1957) grouped H. scandens, H. chinensis (i.e. H. pottingeri), and a host of other arguably distinct taxa complex into one species, H. scandens took priority. This has caused great confusion in Western gardens, where in the later 20th century the name might signify any member of the complex. East Asian floras have tended not to adopt this extreme view (eg. Li 1963; Ohwi 1965; Wei & Bartholomew 2001; Ohba 2001).

H. scandens seems to be less important than H. luteovenosa in Japanese gardens, with far fewer selections made. Nobody knows when it was first grown in the West, but it is said to have been in Sir John Ross’s early 20th century plant collection at Rostrevor House, Northern Ireland (Bean 1981). Bean was still able to say that it was ‘scarcely known in this country and nothing can be said about its garden value’ – this might easily apply to the entire complex, and we cannot be certain which of these weakly delimited species was grown. Crûg Farm made a long list of commercial collections from Honshu, Kyushu and Shikoku in the 1990s, under BSWJ numbers (Crûg Farm Plants 2024): none have made much impact. It is recorded at Sonoma Botanical Garden, California, from W&H 834 and at the US National Arboretum under PCC18-HON-056 (both from Honshu – Quarryhill Botanical Garden 2024; US National Arboretum 2024).