Rhododendron pentaphyllum Maxim.

Bull. Acad. Sci. St Petersbourg, ser. 3, 31:65 (1887).

WFO ID: wfo-0000400196

IPNI ID: urn:lsid:ipni.org:names:333062-1

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Description

Shrub or small tree to 4(-8)m tall; young twigs reddish brown, glabrous to

        sparsely covered with multicellular eglandular or gland-headed hairs; bark pale

        grey-brown, vertically furrowed; new foliage shoots arising from axillary buds

        associated with foliage leaves of terminal cluster of the previous year's shoot (i.e. just below terminal bud), and from some terminal buds. Vegetative bud scales glabrous abaxially, sparsely unicellular-pubescent adaxially; margin fringed with unicellular hairs, usually with multicellular glandular hairs intermixed, especially just below apical region; lowermost scales with apices similar to those of upper scales, not long aristate. Leaves deciduous, lustrous green adaxially, light green abaxially, often with red-tinged margins on young plants, turning orange to red in autumn, pseudo-verticillate, with (4-5(~7) leaves clustered at apex of shoot. Blade chartaceous, elliptic to obovate, 2.1-6.3 x 1.1-3.8cm; base cuneate to attenuate; apex shortly acuminate to acute or obtuse, with a short mucro; midvein moderately to strongly raised abaxially, secondary, tertiary, and higher order veins slightly raised and forming a clearly visible reticulum; adaxial surface glabrous to sparsely covered with multicellular eglandular hairs, the midvein ± densely covered with unicellular hairs, often with a few multicellular eglandular hairs; abaxial surface glabrous to very sparsely unicellular-pubescent near base of blade, the lateral surface of midvein sparsely to densely covered with long, ± straight to crisped, unicellular hairs toward base, often with scattered multicellular eglandular and gland-headed hairs, the secondary veins glabrous, to sparsely unicellular-pubescent at base of blade; margin serrulate, with fringe of long, multicellular eglandular hairs; petiole 2.5-8mm long, sparsely unicellular-pubescent adaxially and these hairs associated with very long, multicellular eglandular hairs, often also a few gland-headed 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 before, or rarely with, the leaves; inflorescence a reduced raceme of 1 or 2 flowers. Pedicels 6-16mm long, glabrous or moderately covered with multicellular gland-headed hairs. Calyx lobes broadly to narrowly triangular to ovate, 0.5-5 x 1.2-1.6mm; apex attenuate, acuminate, or acute, to rounded; margin entire to slightly erose, glabrous to fringed with unicellular hairs, the hairs often irregularly spaced or limited to tuft(s) at apex; adaxial surface glabrous; abaxial surface glabrous. Corolla pink to deep rose, with red-brown spots on upper three lobes or limited to upper lobe, occasionally spots lacking, fragrant, zygomorphic, rotate-campanulate, the tube much shorter than the limb and gradually expanding into it; corolla lobes all±sfmilar, 1.2-2.6 x 1.1-2.5cm; corolla tube 0.4~lcm long; outer surface of corolla glabrous; inner surface of corolla very sparsely unicellular-pubescent towards base. Stamens 10, declinate, variable in length, 0.8~-2.5cm long, included; filaments glabrous throughout to very sparsely to densely covered with flattened unicellular hairs proximally, the shorter filaments tending to be more pubescent than the longer ones. Ovary 3.5-4.5mm long, glabrous; style deciinate, 2.2-2.8cm long, glabrous. Capsules ovoid, 1.2-2x0.5-0.8cm, glabrous. Seeds shiny and dark to light chestnut-brown, angular ovoid to ellipsoid, 2-3.5 x 1-1.5mm; 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, Kyushu)

Altitude

Habitat

In deciduous and coniferous forests and thickets

Nomenclatural History

Azaleapentaphylla (Maxim.) Copeland, Am. Midi. Nat. 30: 595 (1943). Type: Japan, Kyushiu, prov. Osumi, summit, Mt Taka-kuma, Tashiro (holo. LE, n.v.). Rhododendron pentaphyllum Maxim, var. nikoense Komatsu, Icon. PI. Koisikav. 3: 45, t. 168 (1916). Rhododendron nikoense (Komatsu) Nakai in Nakai & Koidz., Trees and Shrubs Japan 1: 68 (1922). Type: Japan, central mountains (n.v.). Rhododendron quinquefolium Bisset & S. Moore var. roseum Rehder in Bailey, Stand. Cycl. Hort. 5: 2947 (1916). Type: n.v. Rhododendron pentaphyllum Maxim, var. shihohanum T. Yamazaki, J. Jap. Bot. 63: 312 (1988). Type: Japan, Shikoku, pref. Kochi, Agawagun Nanokawa, 21 iv 1890, K Watanabe s.n. (holo. TI, 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):19