Hydrangea angustipetala Hayata

This is one of the weakly delineated species of the H. scandens/pottingeri complex, arguably distinct from H. pottingeri which itself is still better known as H. chinensis (the complex as a whole is discussed under H. pottingeri). In cultivation it is a deciduous to evergreen shrub, according to climate, normally with white sterile and yellowish fertile flowers. Neat in habit when young, it sometimes becomes tall and leggy with age. Sepals of sterile flowers are sometimes toothed, sometimes entire. Some large-flowered collections are among the prettiest garden plants in this complex.

Current understanding is that this is a Taiwanese species, if indeed it is distinct from H. pottingeri. First described from Taiwan (Hayata 1911), H. angustipetala has generally been recognized by Taiwanese botanists as differing from Taiwanese H. chinensis (i.e. H. pottingeri) in its hairier, thinner textured leaves and more northerly range on the island (Li 1963). Bleddyn Wynn-Jones reports finding it mainly on forest edges (pers. comm. 2023). The specific epithet is quite unhelpful, since Hayata seems to have been drawing attention to the ‘very narrowed sepals’ of the fertile flowers. Hairy-leaved mainland herbarium specimens once identified as H. angustipetala are nowadays usually assigned to H. chinensis (i.e. H. pottingeri) or other segregate species (Chinese Academy of Sciences 2024). Botanists in mainland China today rarely recognize the species either in Taiwan or on the mainland (Wei & Bartholomew 2001; Chinese Academy of Sciences 2024). Several species described from Taiwan but rarely recognized today seem to belong here, HH. formosana, macrosepala and obovatifolia. These names have resurfaced in a small way attached to some wild collections, as formae, validly published in H. chinensis but apparently not in H. angustipetala. It seems impossible to pin down precisely how they differ from typical H. angustipetala, and we do not recognize them here.

Most introductions to Western gardens identified as H. angustipetala are again from Taiwan, made in the late 20th / early 21st centuries, especially by the Wynn-Joneses of Crûg Farm, and Dan Hinkley. Collections include BSWJ 3423 (see ‘Hoop’), BSWJ 3454, 3476, 3543, 3553, 3667, 3733, 3814, 6787, 6989; DJHT 99021 (see ‘Golden Crane’); and CWJ 12441 (Crûg Farm Plants 2024; Hinkley 2024). From the mainland however, Dan Hinkley’s 2015 Hunan collection DJHHu 15010 (cream flowers, inflorescence 15 cm across, leaves narrow and hairy) is also currently labelled H. angustifolia (Hinkley 2024). Scott McMahan of Atlanta Botanical Garden has also collected the species (Dirr 2021).

This is still a rather experimental subject in Western gardens, and hardiness seems to vary between collections (Dirr 2021). Many thrive in sheltered positions in milder parts of Britain and America’s Pacific Northwest. Light shade, with reasonable soil moisture through the year seems ideal. Several collections grow and flower long-term at White House Farm, Kent, UK (pers. obs.). John Grimshaw considered ‘Hoop’ to be ‘the outstanding hydrangea’ at Windcliff, Dan Hinkley and Robert Jones’ garden overlooking Puget Sound, Washington State, when visiting in 2023 (pers. comm.). Its biggest contribution to gardens may turn out to be as a parent of hybrids such as ‘Ushyd0405’ (RUNAWAY BRIDE SNOW WHITE).