皋月杜鹃，学名：Rhododendron indicum (L.) Sweet，是杜鹃花科、杜鹃属的半常绿灌木。原生分布于日本，中国、朝鲜、缅甸、葡萄牙有传入。

皋月杜鹃是半常绿灌木，高1-2米；分枝多，小枝坚硬，初时密被红褐色糙伏毛，后近于无毛。叶集生枝端，近于革质，狭披针形或倒披针形，长1.7-3.2厘米，稀4.5厘米，宽约6毫米，先端钝尖，基部狭楔形，边缘疏具细圆齿状锯齿，上面深绿色，有光泽，疏被糙伏毛，下面苍白色，中脉在上面凹陷，下面凸出，侧脉在下面微明显，两面散生红褐色糙伏毛；叶柄长2-4毫米，被红褐色糙伏毛。

花芽卵球形，鳞片阔卵形，先端急尖，仅外面及先端具毛。花1-3朵生枝顶；花梗长0.6-1.2厘米，被白色糙伏毛；花萼5裂，裂片椭圆状卵形或近于圆形，长2-3毫米，宽1.5-2毫米，淡绿色，外面及边缘被白色柔毛；花冠鲜红色，有时玫瑰红色，阔漏斗形，长3-4厘米，直径3.7厘米，稀达6厘米，花冠管长1.3厘米，裂片5，广椭圆形，长1.7-2厘米，宽1.6厘米，具深红色斑点；雄蕊5，不等长，长1.6-2.2厘米，比花冠短，花丝淡红色，中部以下被微柔毛，花药深紫褐色，长3毫米，基部具细尖头；子房长3.5毫米，密被亮褐色糙伏毛，花柱长2.3厘米，稀达4.5厘米，比雄蕊长，无毛。

蒴果长圆状卵球形，长6-8毫米，密被红褐色平贴糙伏毛。花期5-6月。

该种与杜鹃相近，不同在于该种的雄蕊5；叶缘具细圆齿状锯齿，易于区别。

亚洲：日本

亚洲：中国、朝鲜、缅甸

欧洲：葡萄牙

皋月杜鹃主要生长在温带生物群落中。

皋月杜鹃一般多用播种或扦插方式繁殖。

皋月杜鹃，花味辛，性温，有毒；有祛风除湿，定痛，杀虫的功效，用于主治风湿痹痛，偏正头痛，跌扑肿痛，龋齿疼痛，皮肤顽癣，疥疮等症。

皋月杜鹃因其花繁叶茂，绮丽多姿，萌发力强，耐修剪。宜在草坪、林缘、溪边、池畔及岩石旁成丛、成片栽植。

“皋月杜鹃”在杜鹃鸣叫时开放，说是杜鹃鸟吐出的血将花染红，因此也称作“杜鹃”。——《雨过天青》

杜鹃花在国际花语中表示“爱的快乐心”。因此送杜鹃的朋友，可以借花表意。不过,中国人却认为“杜鹃蹄血”，有不祥的含意，故此又很忌送杜鹃及种杜鹃花的。

Azalea indica L. in Sp. Pl.: 150 (1753)

Loiseleria indica (L.) Rchb. in Fl. Germ. Excurs. 1: 416 (1831)

Azalea × amoena alba (H.J.Veitch ex Mottet) Anon. in Möller's Deutsche Gärtn.-Zeitung 18: 476 (1903)

Azalea balsaminiflora Carrière in Rev. Hort. (Paris) 54: 432 (1882)

Azalea burgeri Miq. in Ann. Mus. Bot. Lugduno-Batavi 1: 34 (1863)

Azalea calycina Lem. in Jard. FIeur. 3: t. 257 (1853)

Azalea crispiflora Hook. in Bot. Mag. 79: t. 4726 (1853)

Azalea crispiflora var. rosea J.Dix in Proc. Roy. Hort. Soc. London 1: 479 (1861)

Azalea danielsiana Paxton in Paxton's Mag. Bot. 1: 129 (1834)

Azalea decumbens (D.Don ex G.Don) DC. in Prodr. 7: 718 (1839)

Azalea indica var. angustifolia Blume in Bijdr. Fl. Ned. Ind.: 852 (1826)

Azalea indica var. balsaminiflora (Carrière) Kelsey & Dayton in Standard. Pl. Names, ed. 2: 32 (1942)

Azalea indica var. bealei John Edwards in Natl. Gard. Almanack 1855: 312 (1855)

Azalea indica coccinea Reider in Ann. Blumisterei Gartenbesitz. 6: 51 (1830)

Azalea indica var. coccinea (Reider) P.B.Mead in Young Churchman Misc. 3: 80 (1848)

Azalea indica var. copii P.B.Mead in Young Churchman Misc. 3: 80 (1848)

Azalea indica var. crispiflora (Hook.) Van Houtte in Fl. Serres Jard. Eur. 9: 79 (1854)

Azalea indica var. crystallina Verschaff. in Nursery Cat. (Ambroise Verschaffelt) 79: 2 (1866)

Azalea indica var. elegans P.B.Mead in Young Churchman Misc. 3: 80 (1848)

Azalea indica var. floribunda Blume in Bijdr. Fl. Ned. Ind.: 853 (1826)

Azalea indica var. garibaldii Ivery in Proc. Roy. Hort. Soc. London 4: 98 (1864)

Azalea indica imperialis J.Veitch f. in Cat. New Beautiful Pl. 1863: 9 (1863)

Azalea indica var. lateritia Lindl. in Edwards's Bot. Reg. 20: t. 1700 (1834)

Azalea indica narcissiflora John Edwards in Natl. Gard. Almanack 1855: 312 (1855)

Azalea indica var. obtusa (Lindl.) Rehder in L.H.Bailey, Cycl. Amer. Hort. 1: 122 (1900)

Azalea indica var. obtusa-alba (Anon.) Rehder in L.H.Bailey, Cycl. Amer. Hort. 1: 122 (1900)

Azalea indica var. purpurea P.B.Mead in Young Churchman Misc. 3: 80 (1848)

Azalea indica var. rosiflora (Dean) Rehder in L.H.Bailey, Cycl. Amer. Hort. 1: 122 (1900)

Azalea indica var. sinensis Van Houtte in Fl. Serres 20: 151 (1874)

Azalea indica var. spatulata Blume in Bijdr. Fl. Ned. Ind.: 852 (1826)

Azalea indica var. speciosa P.B.Mead in Young Churchman Misc. 3: 80 (1848)

Azalea indica var. stella Veitch in Proc. Roy. Hort. Soc. London 4: 97 (1864)

Azalea indica var. variagata Van Houtte in Hort. Belge 5: 306 (1838)

Azalea indica var. versicolor Low in Proc. Roy. Hort. Soc. London 4: 98 (1864)

Azalea indica virginalis J.Veitch f. in Cat. New Beautiful Pl. 1863: 9 (1863)

Azalea lateritia (Lindl.) André in Belgique Hort. 15: 185 (1865)

Azalea macrantha Bunge in Enum. Pl. China Bor.: 41 (1833)

Azalea obtusa Lindl. in J. Hort. Soc. London 1: 152 (1846)

Azalea obtusa alba H.J.Veitch ex Mottet in Dict. Prat. Hort. 1: 303 (1892)

Azalea ramentacea Lindl. in J. Hort. Soc. London 4: 291 (1849)

Azalea rollissonii T.Moore in Florist & Pomol. 1878: 35 (1878)

Azalea rosiflora Dean in Fl. Mag. (London), n.s., 1880: t. 418 (1880)

Azalea thunbergii (Planch.) André in Belgique Hort. 15: 184 (1865)

Enkianthus biflorus Lour. in Fl. Cochinch.: 277 (1790)

Iposues obovata Raf. in Autik. Bot.: 186 (1840)

Rhododendron × amoenum f. balsaminiflorum (Carrière) Zabel in L.Beissner, E.Schelle & H.Zabel, Handb. Laubholzben.: 384 (1903)

Rhododendron × amoenum var. obtusum (Lindl.) Zabel in Mitt. Deutsch. Dendrol. Ges. 11: 35 (1902)

Rhododendron austrokiusianum Hatus. in J. Jap. Bot. 24: 81 (1949)

Rhododendron balsaminiflorum (Carrière) T.Moore in Florist & Pomol. 1883: 81 (1883)

Rhododendron brachycarpum Zucc. ex Maxim. in Mém. Acad. Imp. Sci. Saint Pétersbourg, Sér. 7, 16(9): 39 (1871), nom. illeg.

Rhododendron buergeri Miq. in Ann. Mus. Bot. Lugduno-Batavi 1: 34 (1863)

Rhododendron crispiflorum (Hook.) Planch. in Fl. Serres Jard. Eur. 9: 83 (1853)

Rhododendron danielsianum Planch. in Fl. Serres Jard. Eur. 9: 79 (1853)

Rhododendron decumbens D.Don ex G.Don in Gen. Hist. 3: 846 (1834)

Rhododendron hispidum D.Don in Edinburgh Philos. J. 6: 48 (1822)

Rhododendron indicum var. balsaminiflorum (Carrière) G.Nicholson in Hand-List Trees Shrubs 2: 53 (1896)

Rhododendron indicum f. balsaminiflorum (Carrière) Rehder in Bibliogr. Cult. Trees: 514 (1949)

Rhododendron indicum var. brachytrichum Komatsu in Bot. Mag. (Tokyo) 31: (18) (1918)

Rhododendron indicum var. crispiflorum (Hook.) C.K.Schneid. in Ill. Handb. Laubholzk. 2: 506 (1911)

Rhododendron indicum f. crispiflorum (Hook.) Rehder in Bibliogr. Cult. Trees: 514 (1949)

Rhododendron indicum var. flore-pleno Drapiez in Hort. Belge 3: 192 (1836), contrary to Art. 23.6. (ICN, 2012).

Rhododendron indicum var. kirishima Millais in Rhododendrons: 193 (1917)

Rhododendron indicum f. laciniatum Makino in Bot. Mag. (Tokyo) 27: 110 (1910)

Rhododendron indicum f. lateritium (Lindl.) Maxim. in Mém. Acad. Imp. Sci. Saint Pétersbourg, Sér. 7, 16(9): 39 (1870)

Rhododendron indicum var. lateritium (Lindl.) DC. in Prodr. 7: 726 (1839)

Rhododendron indicum subvar. lateritium (Lindl.) Makino in Bot. Mag. (Tokyo) 27: 110 (1910)

Rhododendron indicum var. macranthum (Bunge) Maxim. in Mém. Acad. Imp. Sci. Saint Pétersbourg, Sér. 7, 16(9): 39 (1870)

Rhododendron indicum var. obtusum (Lindl.) Maxim. in Mém. Acad. Imp. Sci. Saint Pétersbourg, Sér. 7, 16(9): 40 (1870)

Rhododendron indicum obtusum-album Anon. in Gard. & Forest 9: 394 (1896)

Rhododendron indicum f. otakumi T.Yamaz. in J. Jap. Bot. 41: 348 (1966)

Rhododendron indicum var. rollissonii (T.Moore) Millais in Rhododendrons: 183 (1917)

Rhododendron indicum var. rosiflorum (Dean) Rehder in L.H.Bailey, Stand. Cycl. Hort. 5: 2944 (1916)

Rhododendron kiusianum var. sataense (Nakai) D.F.Chamb. & Rae in Edinburgh J. Bot. 47: 122 (1990)

Rhododendron lateritium (Lindl.) Planch. in Fl. Serres Jard. Eur. 9: 80 (1853)

Rhododendron lateritium var. brachytrichum Nakai in Bot. Mag. (Tokyo) 29: (261) (1915), nom. nud.

Rhododendron macranthum (Bunge) G.Don in Gen. Hist. 3: 846 (1834)

Rhododendron obtusum (Lindl.) Planch. in Fl. Serres Jard. Eur. 9: 80 (1853), nom. illeg.

Rhododendron obtusum f. album (H.J.Veitch ex Mottet) C.K.Schneid. in Ill. Handb. Laubholzk. 2: 506 (1911)

Rhododendron obtusum f. honkirishima Komatsu in Bot. Mag. (Tokyo) 32: (39) (1918)

Rhododendron ramentaceum (Lindl.) Planch. in Fl. Serres Jard. Eur. 9: 81 (1853)

Rhododendron sataense Nakai in Bull. Natl. Sci. Mus. Tokyo 27: 33 (1949)

Rhododendron sieboldii var. minor Miq. in Ann. Mus. Bot. Lugduno-Batavi 1: 33 (1863)

Rhododendron sieboldii var. serrulatum Miq. in Ann. Mus. Bot. Lugduno-Batavi 1: 33 (1863)

Rhododendron thunbergii Planch. in Fl. Serres Jard. Eur. 9: 78 (1853)