1518 



RHODODENDRON 



and if gentle bottom heat can lit* given after callusinj; 

 it -will be of advantage. They root, however, but yiowly, 

 except those of the Javanese kinds, which are mostly 

 propa.u^ateil in this way, since they grow very readily 

 fruni cuttings. 



Lavering is sometimes practiced, especially with the 

 dwarf and" snialldeaved si)ecies, but the layers usually 

 cannot be separated until the second year. 



For the jiropagation of the numerous varieties and 

 hybrids of liardv and half-hardv Rhododendrons graft- 



2105. Azalea Sinensis, to contrast with Rhododendron. 



ing is most extensively employed. JRhododeHdrcni 

 Catawbiense or seedlings of any of its hardy hybrids 

 may be used as stock; M. yiK/.i-iininit is also probaldy 

 as good. In English and Belgian nurseries B. Ponft- 

 cnm, which is inferior in hardiness, is mostly employed 

 as a stock, but this often proves fatal if the grafted 

 plants are transferred to colder climates. 7i*. arboreinn 

 may be used for strong-growing varieties intended for 

 cultivation in the greenhouse or siuith. Veneer- or 

 side-grafting is mostly practiced, and sometimes chd't- 

 and saddle-grafting (see G.C. 111.24:425). The leaves 

 should be removed only partly and the stock not headed 

 back until the following year. The grafting is usually 

 done late in summer or early in spring in the green- 

 house on potted stock without using grafting wax, and 

 the grafted plants kept close and shaded until the union 

 has been completed. If large quantities are to be han- 

 dled the jdauts are sometimes not potted, but taken 

 with a sulUi'ient Jiall of earth, packed close together and 

 covered with' moss. Covering with moss to keep the 

 atnid-iphere moist is also of much advantage if the 

 plants are potted. See Figs. 2107, 2108. 



Distribution of Species. — Ahout 200 species are 

 known, distributed through the colder and temperate 

 regions of the northern hemisphere; in tropical Asia 

 they occur in the mountains and extend as far south as 

 New Guinea and Australia, the greatest segregation 

 heing in the Himalayas and E. Asia; several species 

 closely allied to those of the Malayan Archipelago are 

 found in the Philippine Islands, but are not yet intro- 

 ducer! ; 7 species occur in N. America. The species, with 

 few exceptions, are evergreen. 



Generic Bescripfifni. — Lv^. lepidote. sometimes lejti- 

 dote and pilose, or r|uite g!al)rons or tomentose heneath : 

 fls. pedicelled, in ferminal umbel-like racemes, rarel>' 

 lateral in 1- to few-Hd. clusters; calyx fj-iiarted. often very 



RHODODENDRON 



small: corolla rotate-campanulate to funnel-shaped or 

 sometimes tubular, with n-lO-lobcd limb; stamens .'i-20, 

 usually 10: ovary glalirous, glan<lu!ar, tomentose or lepi- 

 <b)te, iVlO-Ioculed : capsule separating into 5 valves con- 

 taining numerous minute seeds. The Rhododendrons 

 iMjssess l)ut few economic properties. The hardy close- 

 grained wood of the arborescent species is used for 

 fuel; also for construction and for turnery work; the 

 leaves of some species are sometimes used niediciiudly ; 

 those of -/('. arborciiHi are believed to be poisonous to 

 cattle. The tlowers of various species are sometimes 

 made inti) a subacid jelly. Some authors unite Azalea 

 v.'ith Rhododendron, but the two groups are very dis- 

 tinct horticulturally, however closely they may be allied 

 botanically. Azaleas are chiefly deciduous I'lants (.-J. 

 Jnrf/ca mostly evergreen), usually with o exserted sta- 

 mens. Pig. 2105, Azalea iSinensis, also known as Ji'ho- 

 dode>uh'on- Sinensc, shows the difterence in looks be- 

 tween the two grou])s. 



Hybrid Rhododendrons. — I\lany hybrids have been 

 raised and they are now more extensively cultivated 

 than the original species. The hrst hybrid was prob- 

 a1>ly the one raised from B. Pmiticinn, fertilized by a 

 hardy' Azalea, probably A. iiudif/nm ; it originated 

 about 1800, in the nursery of Mr. Thompson, at Mile- 

 end, near London, and was first described and ligured 

 as ii'. Ponticnm, var. deeidvuni (Andrews, Bot. Rep. 

 0:379). Many hybrids of similar origin were afterwards 

 raised. The first hybrid lietween true Rhododendrons 

 was probal.)ly a cross between /i'. Cuiinebiense and 7^. 

 Poiificnni , but it seems not to have attracted much at- 

 tention. It was hy hybri<Uzing the product of this cross 

 with the Himalayan i?. arboreiint introduced about 1820 

 that the hrst plant was raised which became the fore- 

 runner of a countless number of beautiful hybrids. 

 From the appearance of this cross obtained about 182(3, 

 at Highclere, in England, and therefore called B. A Jfa 

 cJarenae, the era of Rhododendron hybrids is to be dated. 

 Figs. 2104 and 210G are common hybrid forms. A sec- 

 ond era in the history of the Rhododendron may be dated 

 from the introduction of a large number of the beau- 

 tiful Sikkim Rho<lodendrons about 1850 and of the 

 Javanese species shortly afterwards. A third era will 

 perhaps be traced from the recent introduction of tht; 

 Yunnan Rhododendrons. Ai^fred Rehdek. 



Hardy Rhododkxdrons. — Rhododendrons, in this ar- 

 ticle, mean the e\"ergreeu sorts, more particularly B. 

 nia.riiHHiii and the hylirid varieties of J?. Caiawbieiise ; 

 in the main, however, the directions for the various ojter- 

 ations apply to tlu' Azalea group and to many other 

 members of the heath family. 



Pro/jagKiii'ii . — Rbododendj'ons are increased by seeds. 

 layers and grafts, and occasionally by cuttings. Seeds 

 should be sown under glass, between January 1 and 

 March 15, in soil one-half peat, one-half pure fine sand, 

 with good drainage. The seeds are small and require 

 no covering, the usual watering after sowing being quite 

 sufficient. A thin layer of sphagnum over the surface of 

 the Seed-pan is good protection from the sun and keeps 

 the soil evenly moist; it should he removed when ger- 

 mination begins. Seeds may also be sown on growing 

 sphagnum, a thin layer being compactly spread above 

 the seed soil and drainage, and an even surface being 

 secured by <di]>iiing. Seed-pans or tlats of convenient 

 size are used and they should be plunged in sphagnum 

 still further to insure even moisture; the temperature 

 of t.he house should be 4r>°-50^ F. Seedlings are pn.ne 

 to damp-ofi' and should be pricki'd-off into fresh soil as 

 soon as they are big enough to handle; wooden pincers, 

 made from a barrel hoop, are handy for this work. They 

 are slow growers and must be tended carefully. Keep 

 under glass, well shaded until the weather is settled. 

 Frames with lath screens nuike good summer quarters. 

 Winter in pits and plant out in frames in peaty soil when 

 large enough. Never let them suffer from dryness. It 

 has been suggested that the seed of 7i*. maximum might 

 be planted on living moss under high -branched trees in 

 swamps where the water does not collect in winter. See 

 Jackson Dawson, on the "Propagation of Trees and 

 Shrulis from Seeds," Trans. Mass. Hort. Soc, 1885, part 

 I, p. 145. 



Layers probably make the i>est plants, autl in the 

 best English nurseries layering is the common method 



