Rhododendron hyperythrum Hayata

Recent DNA evidence indicates that this species is not allied to the remaining members of Rhododendron subsect. Pontica. Further research is required to ascertain its true affinities.

There is clearly confusion in the interpretation of the type of Rhododendron hyperythrum. The sense in which the name is applied in this account follows that proposed by E. H. Wilson and most later authors, and refers to a plant characterized by persistent, red, punctate hair bases on the abaxial surface of the leaf blade. Rhododendron rubropunctatum Hayata belongs to this entity. If, as proposed by Li et al. (in T. C. Huang, Fl. Taiwan, ed. 2, 4: 31. 1998), R. hyperythrum is the correct name for the plant described in the present account as R. pachysanthum (in R. subsect. Maculifera), then a new name will be required for the illegitimate later homonym R. rubropunctatum Hayata.

Shrubs or small trees; young shoots glabrous. Petiole 15–25 mm, glabrous; leaf blade leathery, elliptic-lanceolate to oblong-lanceolate, 7–12 × 2–3.5 cm; base cuneate; margin slightly revolute; apex acute to shortly acuminate; abaxial surface finely red-brown-punctate. Inflorescence racemose-umbellate, ca. 10-flowered; rachis 15–25 mm. Pedicel 3–4.5 cm, sparsely glandular and floccose; calyx lobes 5, ca. 2 mm; margin glandular-ciliate; corolla funnelform-campanulate, white with purple flecks, 3–5 × 3–5 cm; lobes 5, deep; stamens unequal, filaments pubescent at base; ovary densely glandular, ca. 6 mm; style ca. 2.5 cm, glandular in lower half. Fl. Apr.

Open areas. NC Taiwan.

Rhododendron hyperythrum (微笑杜鹃, wei xiao du juan) is a Rhododendron species endemic to north-central Taiwan at 900–1,200 m (3,000–3,900 ft) altitude. It is an evergreen shrub growing to 2.5 m (8.2 ft) in size, with leathery leaves, elliptic-lanceolate to oblong-lanceolate, 7–12 × 2–3.5 cm in size. The flowers are unusual in being pure white.

The plant remains compact in size, and flowers profusely, making it a popular subject for small gardens.