Shrub to 4 m, branches glabrous. Leaves broadly elliptic or oblong, 5–12 x 3–6 cm, apex long acuminate, margin shallowly serrate, minutely hairy on both sides of leaves, dense matted shaggy hairs on midrib of lower surface, lateral veins 5–7 pairs, petiole 0.5–1.2 cm, glabrous. Cymes, axillary or terminal on previous year’s growth, 1–3-flowered. Peduncle to 5–8 mm, hairy, bracts linear 2–8 mm, bracteoles linear, 1–5 mm, both caducous. Calyx tube 5-lobed, radially symmetric, linear, free almost entire length, 0.4–1.2 × c. 0.1 cm, hairy. Corolla funnel-shaped, 2.5–3.5 ×1.6–2 cm, gradually widening above caylx lobes, initially white becoming rose-red outside, deeper pink-red inside, glabrous or hairy outside. Corolla tube 2–2.7 cm, hairy inside, throat yellow, upper part of tube distinctly expanded, corolla 5-lobed, radially symmetric, ovate or oblong-ovate, 0.5–0.8 long (c. 20–25% of length of corolla tube). Stamen longer than corolla, filaments 0.7–1 cm, glabrous; anthers, free, linear 0.5–0.6 cm, yellow. Style longer than corolla, 3–4 cm, glabrous, stigma disc-like, 1–3 mm diameter. Fruit cylindrical, curved 2–3 cm long, dehiscing from apex, glabrous. Seeds broadly oblong, 2 mm long, narrow wings on three sides. Flowers: May to June. (Iwatsuki, K. (ed.), 1993).
Distribution Japan Honshu, Shikoku and Kyushu
Habitat 100 - 2300 m.
RHS Hardiness Rating H4
Taxonomic note The Japanese flora distinguishes two forms, based on of flower colour and one variety also with a form, based on having a smaller corolla and fragrant flowers. forma nivea Sugimoto with white flowers and forma unicolor (Nakai) Hara with flowers that are dark red. Both these forms are consistently one colour and do not change with time. var. amagiensis (Nakai) Hara with a smaller corolla 1.1–1.5 cm and fragrant. Honshu, Izu Peninsula. var. amagiensis forma viridiflava (Nakai) Hara, a form with yellow-green flowers.