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Owen Johnson (2021)
Johnson, O. (2021), 'Diabelia stenophylla' from the website Trees and Shrubs Online (treesandshrubsonline.
A densely-branched shrub to 3 m tall. Shoots glabrous to woolly, with short, long, glandular and curved hairs. Leaves ovate or elliptic, 2–7 × 1–3.5 cm, base rounded to cuneate, tip acute to long-acuminate; glabrescent above, downy beneath espeically under the vein-joints; margin sometimes coarsely serrate; petiole 1–3 mm, usually with spreading hairs. Inflorescence April-June, formed of terminal paired flowers on a peduncle 1–5 mm long; calyx of 5 spreading, reddish sepals, those nearest the shoot sometimes only 2–5 mm long or even absent, the longer sepals lanceolate to oblong; corolla white or sometimes yellowish, 1.6–3.5 cm long; lower part of tube narrowly tubular (1–2 mm wide), the upper part gradually widening to c. 10 mm; mouth bearded and with strong orange markings, upper lobes 5–10 mm long and deeply 2-lobed, lower lip 8–15 mm long, spreading. Stamens nearly as long as the corolla tube. Ovaries very slender, 8–12 mm long. Style sometimes slightly exserted, sparsely hairy. Fruit ripening September-November, sometimes with an apical sterile neck. (Landrein & Farjon 2020).
Distribution China Zhejiang Japan Honshu, Kyushu, Shikoku
Habitat Mountain forests to 1700 m asl, often in rocky places or on limestone.
USDA Hardiness Zone 5
RHS Hardiness Rating H6
Conservation status Least concern (LC)
This species may only be represented in cultivation by its variety (in Landrein’s nomenclatural system) tetrasepala (Koidz.) Landrein (see below). The variety wenzhouensis S.L. Zhou ex Landrein has been named to describe the Chinese population, with leaves glabrous beneath; var. stenophylla itself is confined to the north of Honshu in Japan. The ‘narrow leaves’ of the type specimen, from which Diabelia stenophylla gains its name, are not a characteristic feature of the species as a whole, but the flowers tend to be longer than in other taxa (Landrein & Farjon 2020).
Abelia spathulata var. tetrasepala Koidz.
Abelia tetrasepala (Koidz.) Hara & Kurosawa
Linnaea tetrasepala (Koidz.) Christenh.
Sepals 4 plus a reduced lobe towards the shoot; corolla 3–3.5 cm long (longer than in var. stenophylla). Peduncle 1–3 mm, episepals 1–3 mm long (shorter than in var. stenophylla). (Landrein & Farjon 2020).
RHS Hardiness Rating: H5
USDA Hardiness Zone: 6
This variety grows well to the south of var. stenophylla; its range is similar to that of D. spathulata but it tends to flower about a fortnight earlier so does not interbreed (Landrein et al. 2017). The reduction of the sepals to four mimics the flower-structure of the rather distantly related Zabelia integrifolia, and misidentification, when in fruit, is common (Landrein & Farjon 2020).
This taxon is represented in cultivation in the west by a plant at the Royal Horticultural Society’s Wisley Garden, UK (Royal Botanic Garden Edinburgh 2021).