Rhododendron tephropeploides R.A.Baines & D.F.Chamb., 2021

Baines, R. A., Chamberlain, D. F., Nguyen, V. D. & Quang, B. H., 2021, TWO NEW TAXA OF RHODODENDRON (ERICACEAE) FROM VIETNAM, Edinburgh Journal of Botany 78 (363), pp. 1-8 : 2-4

Rhododendron tephropeploides R.A.Baines & D.F.Chamb. , sp. nov.

(subsect. Tephropepla )

Similar to the allied Rhododendron tephropeplum Balf.f. & Farrer , a species from Northeast India, northern Myanmar and Southwest China, but differs in the dimorphic scales on the lower leaf surfaces; the smaller, 1-mm calyx lobes; the larger funnel-shaped, whitish to pale pink 30–35 mm corollas that are glabrous on the outer surfaces; and the glabrous stamens.

– Type: Cultivated at the RBGE, Logan Botanic Garden (accession number 20150482), 23 iv 2019, Baines 71 (holotype HN, isotype E) . Figures 1 , 2 .

Shrub to 1.2 m tall; bark longitudinally peeling, mahogany. Leaves narrowly elliptic, subacute, apiculate, base cuneate, lamina (30–)50–60 × 20–25 mm, dark green above, lower surface grey, papillose; scales sunk in pits, dense, to twice their diameter apart, dimorphic, the smaller whitish, the larger rufous and scattered; petioles 50–90 mm, densely lepidote, otherwise glabrous. Inflorescence terminal, 3- to 6-flowered, rachis short. Calyx lobes 5-orbicular, c. 1 mm long, scaly below. Corolla funnel-shaped, whitish to pale pink, 30–35 mm long, tube 15 mm long, glabrous on outer and inner surfaces. Filaments glabrous. Ovary lepidote; style impressed, lepidote at base. Capsule ovoid, c.7 × 2–3 mm, densely scaly. Ecology. Temperate montane cloud forest, in wet thin soil with high humus content and high humidity. The surrounding vegetation is characterised by Hydrangea , Illicium and Rhododendron .

Phenology. The above description has been prepared from cultivated plants grown at Logan Botanic Garden from seeds collected in the wild in November 2014. The normal flowering time is mid to late April.

Conservation status. Data Deficient (DD) ( IUCN Standards and Petitions Subcommittee, 2019). Two populations were discovered on Phan Xi Păng Mountain. One of these was at threat from erosion near a public path.

Cultivation. Rhododendron tephropeploides should be grown in partial shade but will tolerate exposed conditions down to a minimum temperature of approximately –8°C. It requires damp, acidic soils that are freely draining but high in organic matter. When propagated from seed it can produce flowers in its third year and should reach a maximum height of 2 m.

Additional specimen examined. VIETNAM. Lào Cai Province: Sa Pa District, Phan Xi Păng Mountain , 2605 m, 22°19.208′N, 103°46.191′E [22°19′12.46′′N, 103°46′11.46′′E], 1 xi 2014, Baines et al. HNE 162 (source of seeds for RBGE accession 20150482) (E, HN, K) .

The differences between Rhododendron tephropeploides and R. tephropeplum are summarised in the Table.

Figures

Figure 1. Rhododendron tephropeploides R.A.Baines & D.F.Chamb., sp. nov. RBGE accession no. 20150482 flowering at Logan Botanic Garden. Photographs: R. A. Baines.

Figure 2. Rhododendron tephropeploides R.A.Baines & D.F.Chamb., sp. nov. A, Flowering stem in cultivation; B, floral parts highlighting stigma, style and minimal calyx; C, floral parts highlighting stamens; D, adaxial leaf surfaces and petioles; E, abaxial leaf surfaces and petioles; F, abaxial view of flowering stem in cultivation; G, habitat. Photographs: L. Wilson.