RHODODENDRON 



2931 



minute seeds. About 350 species are known, distrib- 

 uted through the colder and temperate regions of the 

 northern hemisphere; in Trop. Asia they occur in the 

 mountains and extend as far south as New Guinea and 

 Austral., the greatest segregation being in Cent, and 

 W. China and the Himalayas; several species closely 

 allied to those of the Malayan Archipelago are found 

 in the Philippine Isls. but are not yet intro.; 16 species 

 occur in X. Amer. The rhododendrons possess but 

 few economic properties. The hardy close-grained 



3378. A common hybrid form of garden rhododendron. ( X Ji) 



wood of the arborescent species is used for fuel; also 

 for construction and for turnery work; the Ivs. of some 

 species are used medicinally; those of R. arboreum and 

 other species are believed to be poisonous to cattle. 

 In India the fls. of various species are sometimes made 

 into a subacid jelly. The honey obtained from the 

 fls. is believed to be poisonous. 



The rhododendrons belong to our most ornamental 

 and most beautiful flowering shrubs and are often com- 

 pletely covered with their showy trusses of brilliantly 

 and variously colored flowers and the evergreen species 

 are attractive throughout the whole year with their 

 handsome usually large foliage. They grow best in a 

 peaty or porous loamy soil, which does not contain 

 lime and always retains a sufficient amount of moisture ; 

 they like as a rule half-shaded positions. In regard to 

 their culture and particular ornamental qualities, they 

 may be divided into three horticultural groups: Ever- 

 green rhododendrons, hardy deciduous azaleas, and 

 Indian azaleas. 



Evergreen rhododendrons. 



Here belong the largest number of species comprising 

 the two sections Lepidorhodium and Leiorhodium. 

 Although most of the species are hardy only in 

 warm temperate regions, there are many which are 

 hardy at least as far north as Massachusetts. They are 

 R. maximum, R. cataicbiense, R. caucasicum, R. brachy- 

 carpum, R. Metternichii, R. Smirnovii, R. mueronulatum, 

 R. dahuricum, R. micranthum, R. lapponicum, R. fer- 

 rugineum, R. hirsutum, R. Kotschyi, R. carolinianum, R. 

 minus, and probably also R. chrysanthum, R. Prze- 

 waUeH, R. campanulatum, R. californicum, R. Ungemii, 

 and most of the small-leaved Chinese species. Some- 

 what more tender are R. ponticum, R. niveum, R. 

 Hodgsonii, R. Thomsonii, R. Anlhopogon and many of 

 the recently introduced Chinese species, as R. discolor, 

 R. oreodoxa, R. decorum. South of Philadelphia such 



species as R. cinnabarinum, R. glaucum, R. cUiatum, R. 

 Fortunei, R. lepidotum, R. CoUettianum, and the Yunnan 

 species, as R. yunnanense, R. irroratum, and R. racemo- 

 sum, are probably hardy; also R. arboreum, R. barbatum, 

 R. Falconeri, R. Keysii, R. triflorum, and R. Wrightii in 

 very sheltered positions. Species like R. Dalhousise, 

 R. Edgeifforthii, R. Griffithianum, R. formosum, R. 

 Maddenii, R. Nuttdilii, and R. pendulum stand only a 

 few degrees of frost. The Javanese species, as R. 

 javanicum, R. jasminiflorum, R. Brookeanum and R. 

 Lobbii grow and bloom continually and stand no frost 

 at all. 



Variation in height. Most of the species are shrubby; 

 a few only, and these mostly Himalayan species, grow 

 into small or medium-sized trees, attaining 60 feet in the 

 case of R. barbatum, 40 feet in R. grande and R. arbor- 

 eum, 30 feet in R. Falconeri and R. maximum. A num- 

 ber of northern and alpine species always 

 remain dwarf, as R. ferrugineum, R. hirsutum, 

 R. lapponicum, R. virgatum, R. lepidotum, R. 

 racemosum, and others. A few Himalayan and 

 Chinese species and most of the Malayan 

 species are often epiphytal and grow on 

 branches of large trees like orchids; e. g., 

 R. Dalhousix, R. pendulum, R. Nuttattii, R. 

 moupinense. 



Hybrid rhododendrons. Many hybrids have been 

 raised and they are now more extensively cultivated 

 than the original species. The first hybrid was probably 

 the one raised from R. ponticum, fertilized by a hardy 

 azalea, probably A. nudiflorum; it originated about 1800, 

 in the nursery of Thompson, at Mileend, near Lon- 

 don, and was first described and figured as R. ponti- 

 cum yar. deciduum (Andrews, Bot. Rep. 6:379). Many 

 hybrids of similar origin were afterward raised for 

 which the name Azaleodendron has been proposed by 

 Rodigas. The first hybrid between true rhododendrons 

 was probably a cross between R. catawbiense and R. 

 ponticum, but it seems not to have attracted much 

 attention. It was by hybridizing the product of this 

 cross with the Himalayan R. arboreum introduced about 

 1820 that the first plant was raised which became the 

 forerunner of a countless number of beautiful hybrids. 

 From the appearance of this cross, obtained about 

 1826, at Highclere, in England, and therefore called R. 

 altaclarense, the era of rhododendron hybrids is to be 

 dated. Figs. 3378 and 3379 are common hybrid forms. 

 A second era in the history of the rhododendron may 

 be dated from the introduction of a large number of 

 the beautiful Sikkim rhododendrons about 1850, among 

 them species like R. Griffithianum which entered into 

 the parentage of many of the most striking tender 

 hybrids, and from the introduction of the Javanese 

 species shortly afterward. A third era will perhaps be 

 traced from the recent introduction of the Chinese 

 rhododendrons. 



Their place in ornamental planting. Rhododendrons 

 are equally effective and desirable as single specimens 

 on the lawn as when massed in large groups, and are 

 especially showy when backed by the dark green foliage 

 of conifers, which at the same time afford a most 

 advantageous shelter. The dwarf species, which are 

 mostly small-leaved and flower at a different time, 

 should not be grouped with the large-leaved ones, as 

 they dp not harmonize with them; however, they are 

 exceedingly charming plants for rockeries or in groups 

 with other smaller evergreens. It is certainly true that 

 the rhododendrons have not yet received the attention 

 they deserve. They are still far from being as popular as 

 they are in England. The beautiful Himalayan species 

 and their numerous hybrids are still almost unknown 

 in this country, although without doubt they could be 

 grown as well outdoors in the Middle and South Atlantic 

 states as they are in England, if the right situation 

 were chosen. Formerly it was considered impossible to 

 grow the beautiful hardy hybrids in the New England 



