Hydrangea kwangsiensis Hu

This southern Chinese species with lanceolate leaves and lacecap inflorescences with white sterile and blue or pink fertile flowers is possibly in cultivation, but identifications are still uncertain. Anything offered under this name is likely to suit light shade, or at least some respite from sun in the middle of the day, a moist but well drained soil, and a mild, maritime climate as in the British Isles or the Pacific Northwest.

Although only described from south-central China (Wei & Bartholomew 2001), the cultivated plants occasionally placed here are from collections in northern Vietnam. Morphologically H. kwangsiensis has much in common with H. stylosa and H. indochinensis, (see further discussion under those species), sharing their essentially inferior ovary and glabrous upper leaf surface. Like the type of H. indochinensis, it has lanceolate leaves with reflexed margins (not apparent in the collections listed below). In theory, the hairier lower leaf surface would seem to be a distinguishing feature of H. kwangsiensis, but indumentum does not seem to correlate well with other supposed identification characters in this group (pers. obs.). While H. davidii (itself a hard thing to pin down) might seem to be distinct in its much more superior ovary, in practice this is not always clear-cut. Brian Bartholomew (in Wei & Bartholomew 2001) points out a similarity to H. stenophylla (a name yet to trouble gardeners), and recommends further study of the two species. A great number of images of wild H. kwangsiensis on the PlantPlus website, mainly from Guangdong and Hunan, give a rather consistent picture of a shrub with a glossy upper leaf surface, a glaucescent to glaucous underside (not a common Hydrangea feature), and sharply spreading stamens giving the look of a 10-spoked wheel at maturity (Chinese Academy of Sciences 2024).

The relationships of H. kwangsiensis are not entirely clear. De Smet et al. (2015) had no molecular data available, and merely speculated that it might belong to Section Stylosae. One molecular study has included H. kwangsiensis and found it to be rather an outlier within the Hydrangea II clade, as sister to a clade comprising Sections Chinenses and Dichroa (Yang et al. 2024): they place it in its own Section Kwangsienses.

The following 21st century collections from N Vietnam have all sometimes been placed here, as well as in H. indochinensis: FMWJ 13187, BSWJ 11609, BSWJ 11717 (Far Reaches Farm 2024; Crûg Farm Plants 2024). FMWJ 13187 has impressed at Far Reaches Farm, Washington State, the flowers having ‘that little sumpin’ sumpin’ that made this the staff favorite’ (Far Reaches Farm 2024).

Confusion reigns. It seems unlikely that southern Chinese and northern Vietnamese plants of this type in gardens can confidently named until botanists have better understood variation, species limits and relationships in the wild.