Rhododendron quinquefolium Bisset Sc S. Moore

J. Bot. 15: 292 (1877).

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Description

Shrub or small tree to 6(-8)m tall; young twigs dark to reddish brown,

        glabrous; bark grey-brown, corky, fissured into irregular ± longitudinally elongated

        plates; new foliage shoots arising from axillary buds associated with the lowest scaly

        leaves of the present year's shoots (i.e. within the terminal bud), and from some terminal buds. Vegetative bud scales glabrous abaxially, sparsely unicellular-pubescent adaxially; margin fringed with unicellular hairs, with multicellular glandular hairs intermixed, especially just below apical region; lowermost scales with long aristate apices or rudimentary blades. Leaves deciduous, dark green adaxially, pale green abaxially, often tinged with reddish purple along margin, turning red in autumn, pseudo-verticillate, with (3-) 5 leaves clustered at apex of shoot. Blade membranaceous, broadly rhombic-elliptic to obovate, 1-5.8 x0.6-3.6cm; base cuneate to attenuate; apex acute to rounded, occasionally slightly emarginate, with a short mucro; midvein and secondary veins slightly to moderately raised and visible abaxially; adaxial surface sparsely covered with straight to curled unicellular hairs to glabrous, sometimes also with scattered multicellular eglandular hairs, especially near midvein or margin, the midvein ± densely covered with flattened, + straight to curled unicellular hairs, sometimes with scattered multicellular gland-headed hairs and/or eglandular hairs; abaxial surface glabrous to moderately unicellular-pubescent, especially at base of blade, the midvein or its lateral surfaces sparsely to densely covered with long, straight to crisped, unicellular hairs, especially towards base, or such hairs lacking, often with scattered multicellular gland-headed hairs and eglandular hairs, the secondary veins glabrous to sparsely unicellular-pubescent, especially at base of blade; margin entire, with fringe of unicellular hairs, often with multicellular eglandular hairs intermixed; petiole l-5mm long, very sparsely to densely covered with unicellular hairs, sometimes with a few multicellular gland-headed and/or eglandular hairs, the base of petiole slightly expanded at point of attachment. Flower bud scales larger, but otherwise similar to those of vegetative buds. Flowers appearing with the leaves; inflorescence a reduced raceme of 1 to 3 flowers. Pedicels 6-30mm long, glabrous to moderately covered with multicellular gland-headed or eglandular hairs. Calyx lobes narrowly triangular, 0.8-3 x 0.5-1.5mm; apex acute or acuminate to rounded; margin usually fringed with multicellular gland-headed and/or eglandular hairs, occasionally these very sparse and margin essentially glabrous, sometimes with unicellular hairs; adaxial surface glabrous; abaxial surface glabrous, rarely with a few multicellular gland-headed hairs at extreme base. Corolla white, with greenish spots on upper three lobes, slightly zygo-morphic, broadly rotate-funnelform, the tube shorter than the limb and gradually expanding into it; corolla lobes ± all similar, 1-2 x 0.8-1.7cm; corolla tube 0.7-1.2cm long; outer surface of corolla glabrous; inner surface of corolla sparsely unicellular-pubescent towards base. Stamens 10, declinate, variable in length, 0.9-2.2cm long, included; filaments glabrous distally, becoming densely covered with flattened unicellular hairs proximally. Ovary 2-3.5mm long, densely covered with unicellular hairs to nearly glabrous, with unicellular hairs limited to apex; style declinate, 1.3-2.5cm long, glabrous distally, often sparsely covered with unicellular hairs on proximal portion. Capsules ovoid to±cylindric, often curved, 0.9-1.6x0.4-0.6cm, glabrous to sparsely unicellular-pubescent, especially at apex. Seeds light brown, angular-ovoid to ellipsoid, 2.5-3 x0.7-lmm; testa tightly appressed to body, tails lacking, the cells elongate. Cotyledons with multicellular gland-headed hairs along margin and well-developed reticulate venation.

Distribution

Japan (Honshu, Shikoku)

Altitude

Habitat

In deciduous or coniferous forests and thickets

Nomenclatural History

Azalea quinquefolia (Bisset & S. Moore) Olmsted, Coville, & Kelsey, Stand. PI. Names 27 (1923). Type: Japan, Honshu, Nikko, 23 v 1876, Bisset 233 (lecto., designated here, E). Rhododendron quinquefolium Bisset & S. Moore f. speciosum N. Yonezawa, J. Phytogeogr. Taxon. 35(2): 101 (1987). Type: Japan, Honshu, pref. Shiga, Mt Hira, c.l020m, 24 v 1987, N. Yonezawa s.n. (nolo., KANA #121504, n.v.).

Notes

References

Judd, W.S. & Kron, K.A. (1995) A Revision of Rhododendron VI. Subgenus Pentanthera (Sections Sciadorhodion, Rhodora and Viscidula). Edinburgh Journal of Botany 52(1):16