Rhododendron luteum Sweet

Hort. Brit. ed. 2, 343 (1830), non Azalea lutea L., Sp. PL ed. 1,1:

150 (1753); based on Azalea ponticaL. (1753), q.v.

WFO ID: wfo-0000399990

IPNI ID: urn:lsid:ipni.org:names:332817-1

Verified by:

Description

Shrub or small tree to 2m tall, usually non-rhizomatous; young twigs red-brown, rarely yellow-brown, densely covered with unicellular hairs and multicellular gland-tipped hairs, rarely also with multicellular eglandular hairs, or with only multicellular gland-tipped and eglandular hairs. Vegetative bud scales glabrous, rarely sparsely covered with unicellular hairs abaxially; margin glandular ciliate. Leaf blade membranaceous, ovate or obovate to elliptic, (6.4-)7.6-12.0(-14.6) x (1.6-)2.1-3.4(-4.2)cm; base acute to oblique; apex acute to obtuse, often mucronate; adaxial surface sparsely to densely covered with multicellular gland-tipped hairs, or rarely with multicellular eglandular hairs, the midvein densely covered with unicellular hairs; abaxial surface glabrous, occasionally glaucous, the veins raised and prominent beneath, rarely sparsely to densely covered with unicellular hairs, or with multicellular gland-tipped and eglandular hairs, or all three types of hairs, the midvein sparsely to densely covered with unicellular and multicellular gland-tipped hairs, rarely lacking the unicellular hairs; margin entire, ciliate with multicellular eglandular hairs above and gland-tipped hairs below; petiole 0.3-0.6(-0.8)cm long, densely covered with unicellular hairs and multicellular gland-tipped hairs, rarely with multicellular eglandular and glandular hairs. Flower bud scales chestnut brown; abaxial surface glabrous, occasionally sparsely to densely covered with unicellular hairs; margin glandular. Flowers appearing before or with the leaves; inflorescence a shortened raceme of 9 to 17 flowers. Pedicels (0.8-)0.9-1.8(-2.4)cm long, densely covered with multicellular gland-tipped hairs, occasionally with unicellular hairs and multicellular gland-tipped hairs. Sepals less than 0.1-0.4(-0.7)cm long, varying in length on the same flower; margins glandular-fimbriate; abaxial surface sparsely covered with multicellular gland-tipped hairs, occasionally with unicellular hairs, rarely glabrous. Corolla yellow with a darker yellow blotch on the upper corolla lobe, fragrance sweet, the tube longer than the limb and gradually expanding into it; upper corolla lobe (1.3-)1.4-2.0(-2.4) x (0.8-)0.9-1.5(-2.0)cm wide; lateral lobes (1.3-)1.6-2.2(-2.5) x (0.5-)0.7-l.l(-1.2)cm; corolla tube (1.2-)1.3-2.0(-2.4)cm long, 0.2-0.4(-0.5)cm wide at base; outer surface of corolla sparsely to densely covered with multicellular gland-tipped hairs, or also with unicellular hairs, the gland-tipped hairs continuing up the corolla lobes; inner surface of corolla glabrous, rarely sparsely covered with unicellular hairs. Stamens (3.2-)3.4-4.4(-5.0)cm long, with dense terete or flattened unicellular hairs on proximal (1.6-)1.7-2.3(-2.5)cm of filament, exserted (1.4-)1.8-2.7(-3.0)cm beyond throat of corolla. Style (3.5-)3.7-5.0(-5.4)cm long, exserted (2.2-)2.4-3.8(-4.2)cm beyond throat of corolla, with dense unicellular hairs on proximal 0.2-0.6(-l .0)cm of style; stigma 0. l-0.2cm wide. Ovary (0.2-)0.3-0.4cm long, (0. l-)0.2-0.3cm wide at the base, sparsely covered with multicellular hairs, often with flattened or terete unicellular hairs in a tuft at the apex. Capsules (1.3-)1.5-2.1(-2.2) x 0.4-0.7(-0.8)cm, broadly ovate, sparsely covered with unicellular hairs and sparsely to moderately covered with multicellular gland-tipped hairs. Seeds pale to dark chestnut brown, ovate or effiptic to fusiform, (2.4-)2.8-3.8(-4.8) x (0.5-)0.7-l .2(-l .5)mm, body (1.1-) 1.3-1.8(-2.0) x (0.3-)0.4-0.6(-0.7)mm; testa expanded and dorsiventrally flattened, surrounding the body, the cells elongate, with tapered end-walls

Distribution

Caucasus: Former Soviet Union, Turkey, and isolated populations in Poland and former Yugoslavia.

Altitude

Habitat

Open wooded slopes, along streams and in swampy areas, shores of the Black Sea

Nomenclatural History

AzaleaponticaL.,Sp.Pl.ed. 1,1:150 (n53).Anthodendronponticum(L.)Rchb. in Mossier, Handb. Gewachsk. 1: 309 (1827). Rhododendron ponticum (L.) Schreb. ex DC, Prodr. 7: 718 (1839), non L., Sp. PI. ed. 1,1: 154 (1753). Type: Elus. in Buxbaum, Plant. Minus Cogni. Cent. 5: 36, fig. 69 (1740). RhododendronflavumG. Don, Gen. Syst. 3: 847 (1834), nom. illeg.; based on Azaleapontica L. (1753) [ = R. luteum Sweet (1830)]. Azalea flava Hoffmanzegg, Verz. Pflanzenkult. Nachtr. 2: 62 (1826). Type: n.v. Azalea pontica L. var. autumnalis C Koch, Linnaea 17: 281 (1843). Type: n.v. Rhododendron flavum G. Don var. macranthum Bean, Trees and Shrubs Brit. Isles 2: 357 (1914). R. luteum Sweet var. macranthum Wilson, Monogr. Azaleas 105 (1921). Type: n.v.

Notes

References

Kron, K.A. (1993) A Revision of Rhododendron Section Pentanthera. Edinburgh Journal of Botany 50(3):314