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Rhododendron (Greek, rhodon and dendron, rose-tree; the Rhododendron of the ancient writers is Nerium). Ericaceae. Including Azalea which most botanists consider inseparable from Rhododendron, but horticulturists may be inclined to retain Azalea for the deciduous species and to use the Azalea names given in parentheses. Highly ornamental woody plants, chiefly grown for their beautiful flowers and many species also for their handsome foliage.

Rhododendron (Greek, rhodon and dendron, rose-tree; the Rhododendron of the ancient writers is Nerium). Ericaceae. Including Azalea which most botanists consider inseparable from Rhododendron, but horticulturists may be inclined to retain Azalea for the deciduous species and to use the Azalea names given in parentheses. Highly ornamental woody plants, chiefly grown for their beautiful flowers and many species also for their handsome foliage.

Hardy varieties.—The following varieties have proved  in the vicinity of Boston and may be recomended for planting in similar climates and for experimental trial farther north. They are mostly hybrids of R.    with R. maximum, R. ponticum, R. caucasicum and with some infusion of R. arboreum and perhaps a few other species. As in most of them the parentage of R. catawbiense is the most predominant, they are all usually called "catawbiense hybrids." Choice kinds are (those marked with an asterisk have proved the hardiest): Album elegans, blush, changing to white; Album grandiflorum, blush, changing to white, flowers larger, less spotted; Alexander Dancer, bright rose, paler in center; Atrosanguineum, rich blood-red; August Van Geert, bright carmine, spotted dark purple; Bacchus, crimson, large flowers; Bicolor, purplish pink, spotted; Blandianum, rosy crimson (H.F. 1859:153); Bluebell, blush, with light purplish margin; Boule de Neige, white, early; Caractacus, deep crimson; Charles Bagley, cherry-red.; Charles Dickens, dark red, spotted brown, one of the most striking red ones; Caerulescens, pale lilac; Coriaceum, white, spotted yellow, dwarf and free-blooming; Crown Prince, carmine, spotted greenish yellow; Delicatissimum, blush, edged pink, changing to almost white, late (Gn. 63, p. 415); Edward S. Rand, rich scarlet; Everestianum, rosy lilac with crisped edges, excellent habit and very free-flowering (G. 26:103); F. L. Ames, white center, edged pink; F. L. Olmsted, pink; Giganteum, bright rose, large clusters; Glennyanum, white, suffused with pink (G.M. 44:355; 48:565); Gomer Waterer, blush-pink; Grandiflorum, clear rose; Guido, deep crimson; Hannibal, rosy carmine; Henrietta Sargent, pink; Henry W. Sargent, crimson, large clusters; H. H. Hunnewell, rich crimson; John Waterer, dark crimson; J. D. Godman, carmine, distinctly spotted; Kettledrum, rich crimson; King of Purples, purple, spotted dark brown; Lady Armstrong, rose-red, paler in center, distinctly spotted; Lady Clermont, rosy scarlet; Lady Frances Crossley, salmon-pink; Lady Gray Egerton, delicate lilac, spotted greenish brown; Lee's Purple, purple; Madam Carvalho, blush, changing to pure white; Melton, rich purple; Mrs. C.S. Sargent, similar to Everestianum, but pink; Mrs. Milner, rich crimson; Norma, pink; Old Port, plum-color; Princess Mary of Cambridge, white with purple margin; Purpureum crispum, lilac-purple, spotted greenish; Purpureum grandiflorum, purple, large clusters; R. S. Field, scarlet; Ralph Sanders, rich purplish crimson; Rosa mundi, white slightly flushed with yellow spots, dwarf (Gn. 63, p. 369); Roseum elegans, rosy lilac, dwarf; Scipio, rose with deep spot; Sefton, deep maroon, large clusters; Wellsianum, blush, changing to white.

Hardy varieties.—The following varieties have proved  in the vicinity of Boston and may be recomended for planting in similar climates and for experimental trial farther north. They are mostly hybrids of R.    with R. maximum, R. ponticum, R. caucasicum and with some infusion of R. arboreum and perhaps a few other species. As in most of them the parentage of R. catawbiense is the most predominant, they are all usually called "catawbiense hybrids." Choice kinds are (those marked with an asterisk have proved the hardiest): Album elegans, blush, changing to white; Album grandiflorum, blush, changing to white, flowers larger, less spotted; Alexander Dancer, bright rose, paler in center; Atrosanguineum, rich blood-red; August Van Geert, bright carmine, spotted dark purple; Bacchus, crimson, large flowers; Bicolor, purplish pink, spotted; Blandianum, rosy crimson (H.F. 1859:153); Bluebell, blush, with light purplish margin; Boule de Neige, white, early; Caractacus, deep crimson; Charles Bagley, cherry-red.; Charles Dickens, dark red, spotted brown, one of the most striking red ones; Caerulescens, pale lilac; Coriaceum, white, spotted yellow, dwarf and free-blooming; Crown Prince, carmine, spotted greenish yellow; Delicatissimum, blush, edged pink, changing to almost white, late (Gn. 63, p. 415); Edward S. Rand, rich scarlet; Everestianum, rosy lilac with crisped edges, excellent habit and very free-flowering (G. 26:103); F. L. Ames, white center, edged pink; F. L. Olmsted, pink; Giganteum, bright rose, large clusters; Glennyanum, white, suffused with pink (G.M. 44:355; 48:565); Gomer Waterer, blush-pink; Grandiflorum, clear rose; Guido, deep crimson; Hannibal, rosy carmine; Henrietta Sargent, pink; Henry W. Sargent, crimson, large clusters; H. H. Hunnewell, rich crimson; John Waterer, dark crimson; J. D. Godman, carmine, distinctly spotted; Kettledrum, rich crimson; King of Purples, purple, spotted dark brown; Lady Armstrong, rose-red, paler in center, distinctly spotted; Lady Clermont, rosy scarlet; Lady Frances Crossley, salmon-pink; Lady Gray Egerton, delicate lilac, spotted greenish brown; Lee's Purple, purple; Madam Carvalho, blush, changing to pure white; Melton, rich purple; Mrs. C.S. Sargent, similar to Everestianum, but pink; Mrs. Milner, rich crimson; Norma, pink; Old Port, plum-color; Princess Mary of Cambridge, white with purple margin; Purpureum crispum, lilac-purple, spotted greenish; Purpureum grandiflorum, purple, large clusters; R. S. Field, scarlet; Ralph Sanders, rich purplish crimson; Rosa mundi, white slightly flushed with yellow spots, dwarf (Gn. 63, p. 369); Roseum elegans, rosy lilac, dwarf; Scipio, rose with deep spot; Sefton, deep maroon, large clusters; Wellsianum, blush, changing to white.

For greenhouse culture, the most successful way, especially with the taller-growing species, like R. arboreum, R. Griffuhianum, R. barbatum, and R. Falconeri, is to plant them out in a porous peaty soil provided with good drainage. If grown in pots, a sandy compost of leaf-soil and peat, with an addition of some fibrous loam, will suit them. The pots, which should never be too large, must be well drained and the plants freely watered during the summer, while during the winter water must be carefully applied. The Himalayan species and their hybrids will do well in a cool greenhouse, where the temperature is kept a few degrees above freezing-point during the winter. The Javanese species and hybrids, however, on account of their continual growing and blooming, require a warmer greenhouse and must have a minimum temperature of 50° during the winter. They like a moist atmosphere and should be freely syringed in warm weather. In potting them, their epiphytal habit must be borne in mind, and the soil should consist mainly of good fibrous peat broken into pieces, with a liberal addition of sand and broken charcoal. The soil should never be allowed to become dry. They are readily propagated by cuttings with bottom heat in the warm propagating-house. The Javanese rhododendrons are especially valuable for their continual blooming during the winter and the brilliant color of their flowers. A large number of beautiful hybrids have been raised; the following are a

For greenhouse culture, the most successful way, especially with the taller-growing species, like R. arboreum, R. Griffuhianum, R. barbatum, and R. Falconeri, is to plant them out in a porous peaty soil provided with good drainage. If grown in pots, a sandy compost of leaf-soil and peat, with an addition of some fibrous loam, will suit them. The pots, which should never be too large, must be well drained and the plants freely watered during the summer, while during the winter water must be carefully applied. The Himalayan species and their hybrids will do well in a cool greenhouse, where the temperature is kept a few degrees above freezing-point during the winter. The Javanese species and hybrids, however, on account of their continual growing and blooming, require a warmer greenhouse and must have a minimum temperature of 50° during the winter. They like a moist atmosphere and should be freely syringed in warm weather. In potting them, their epiphytal habit must be borne in mind, and the soil should consist mainly of good fibrous peat broken into pieces, with a liberal addition of sand and broken charcoal. The soil should never be allowed to become dry. They are readily propagated by cuttings with bottom heat in the warm propagating-house. The Javanese rhododendrons are especially valuable for their continual blooming during the winter and the brilliant color of their flowers. A large number of beautiful hybrids have been raised; the following are a small selection of them: Balsaminaeflorum, with double pink flowers (Gt. 37, p. 265. G.C. II. 18:230; III. 12:769. J.H. III. 43:151. G.Z. 27:241); Balsaminaeflorum album, with double white flowers (Gn.W. 5:373); Balsaminaeflorum aureum, with double yellow flowers; Brilliant, brilliant scarlet; Ceres, tawny yellow (Gn. 41:845); Diadem, orange-scarlet; Duchess of Connaught, vermilion-red; Duchess of Edinburgh, scarlet with orange-crimson (F.M. 1874:115); Eos, scarlet-carmine (G.C. III. 19:327); Exquisite, large light fawn-yellow flowers (Gn. 56:62); Favorite, satiny rose; Jasminiflorum carminatum, deep carmine (Gn. 41:328); Little Beauty, flowers small, but bright carmine-scarlet (Gn. 56:242); Lord Wolseley, bright orange-yellow, tinted with rose at the margins; Luteo-roseum, flowers satiny rose, suffused with white, center light yellow (G. 33: 313); Maiden's Blush, blush, with yellowish eye (Gn. 16:394); Princess Alexandra, white, faintly blushed; Princess Frederica, yellow, faintly edged rose; Princess Royal, pink; Rosy Morn, bright pink (Gn. 42:164); Taylori, bright pink, with white tube (F. M. 1877:242); Triumphans, crimson-scarlet.

small selection of them: Balsaminaeflorum, with double pink flowers (Gt. 37, p. 265. G.C. II. 18:230; III. 12:769. J.H. III. 43:151. G.Z. 27:241); Balsaminaeflorum album, with double white flowers (Gn.W. 5:373); Balsaminaeflorum aureum, with double yellow flowers; Brilliant, brilliant scarlet; Ceres, tawny yellow (Gn. 41:845); Diadem, orange-scarlet; Duchess of Connaught, vermilion-red; Duchess of Edinburgh, scarlet with orange-crimson (F.M. 1874:115); Eos, scarlet-carmine (G.C. III. 19:327); Exquisite, large light fawn-yellow flowers (Gn. 56:62); Favorite, satiny rose; Jasminiflorum carminatum, deep carmine (Gn. 41:328); Little Beauty, flowers small, but bright carmine-scarlet (Gn. 56:242); Lord Wolseley, bright orange-yellow, tinted with rose at the margins; Luteo-roseum, flowers satiny rose, suffused with white, center light yellow (G. 33: 313); Maiden's Blush, blush, with yellowish eye (Gn. 16:394); Princess Alexandra, white, faintly blushed; Princess Frederica, yellow, faintly edged rose; Princess Royal, pink; Rosy Morn, bright pink (Gn. 42:164); Taylori, bright pink, with white tube (F. M. 1877:242); Triumphans, crimson-scarlet.

Propagation.—All rhododendrons are easily propagated by seeds, which are very small and are sown in spring in pans or boxes well drained and filled with sandy peat. Pots should be well watered previous to sowing. The seeds should be covered only a very little with fine sand or finely cut sphagnum, or merely pressed in and not covered at all. To prevent drying, a glass plate may be placed over the pan or some moss spread over the surface; this, however, must be taken off as soon as the seeds begin to germinate. The seeds also germinate very readily if sown on fresh sphagnum, but in this case they must be pricked off as soon as they can be handled. In any case, it is of advantage to prick off the young seedlings as soon as possible, but if they are not sown too thickly they may remain in the seed-boxes until the following spring. The seedlings of hardy rhododendrons should be placed in coolframes and gradually hardened off; those of greenhouse species remain under glass. Rhododendrons are also sometimes increased under glass by cuttings of half-ripe wood taken with a heel, and if gentle bottom heat can be given after callusing it will be of advantage. They root, however, but slowly, except those of the Javanese kinds, which are mostly propagated in this way, since they grow very readily from cuttings. Layering is sometimes practised, especially with the dwarf and small-leaved species, but the layers usually cannot be separated until the second year. For the propagation of the numerous varieties and hybrids of hardy and half-hardy rhododendrons grafting is most extensively employed. R. catawbiense or seedlings of any of its hardy hybrids may be used as stock; R. maximum is also probably as good. In English and Belgian nurseries R. ponticum, 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. R. arboreum may be used for strong-growing varieties intended for cultivation in the greenhouse or South. Veneer- or side-grafting is mostly practised, and sometimes cleft- and saddle-grafting (see G.C. III. 24:425 and Figs. 3380, 3381). 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 greenhouse 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 handled the plants are sometimes not potted, but taken with a sufficient ball of earth, packed close together and covered with moss. Covering with moss to keep the atmosphere moist is also of much advantage if the plants are potted.

Propagation.—All rhododendrons are easily propagated by seeds, which are very small and are sown in spring in pans or boxes well drained and filled with sandy peat. Pots should be well watered previous to sowing. The seeds should be covered only a very little with fine sand or finely cut sphagnum, or merely pressed in and not covered at all. To prevent drying, a glass plate may be placed over the pan or some moss spread over the surface; this, however, must be taken off as soon as the seeds begin to germinate. The seeds also germinate very readily if sown on fresh sphagnum, but in this case they must be pricked off as soon as they can be handled. In any case, it is of advantage to prick off the young seedlings as soon as possible, but if they are not sown too thickly they may remain in the seed-boxes until the following spring. The seedlings of hardy rhododendrons should be placed in coolframes and gradually hardened off; those of greenhouse species remain under glass. Rhododendrons are also sometimes increased under glass by cuttings of half-ripe wood taken with a heel, and if gentle bottom heat can be given after callusing it will be of advantage. They root, however, but slowly, except those of the Javanese kinds, which are mostly propagated in this way, since they grow very readily from cuttings. Layering is sometimes practised, especially with the dwarf and small-leaved species, but the layers usually cannot be separated until the second year. For the propagation of the numerous varieties and hybrids of hardy and half-hardy rhododendrons grafting is most extensively employed. R. catawbiense or seedlings of any of its hardy hybrids may be used as stock; R. maximum is also probably as good. In English and Belgian nurseries R. ponticum, 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. R. arboreum may be used for strong-growing varieties intended for cultivation in the greenhouse or South. Veneer- or side-grafting is mostly practised, and sometimes cleft- and saddle-grafting (see G.C. III. 24:425 and Figs. 3380, 3381). 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 greenhouse 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 handled the plants are sometimes not potted, but taken with a sufficient ball of earth, packed close together and covered with moss. Covering with moss to keep the atmosphere moist is also of much advantage if the plants are potted.

Other experience with the evergreen rhododendrons. (B. M. Watson.)—Rhododendrons, in this article, mean more particularly R. maximum and the hybrid varieties of R. catawbiense; in the main, however, the directions for the various operations apply to the azalea group and to many other members of the heath family.

Other experience with the evergreen rhododendrons. (B. M. Watson.)—Rhododendrons, in this article, mean more particularly R. maximum and the hybrid varieties of R. catawbiense; in the main, however, the directions for the various operations apply to the azalea group and to many other members of the heath family.

Rhododendrons as a class 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 and one-half pure fine sand, with good drainage. The seeds are small and

Rhododendrons as a class 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 and 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 be removed when germination 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 clipping. Seed-pans or flats of convenient size are used and they should be plunged in sphagnum still further to insure even moisture; the temperature of the house should be 45° to 50° F. Seedlings are prone to damp-off and should be pricked 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 make 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 R. 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 Shrubs from Seeds," in Transactions of the Massachusetts Horticultural Society, 1885, part I, page 145.) Layers probably make the best plants, and in the best English nurseries layering is the common method of propagation. In the United States layering in spring is preferable, but abroad it is practised in both spring and autumn. It is a slow process, but desirable for the hardy hybrids of R. catawbiense. Roots form on wood of almost any age; when removed the layers should be treated as rooted cuttings and carefully grown in well-prepared soil where water and shade are easily furnished. See Layering. See, also, G.F. 6:63 (1893) for an interesting account of layering large plants by burying them to the top.-Grafting is the common method of propagation, and is employed almost universally in continental nurseries. R. ponticum is the usual stock, a free grower and readily obtained from seeds. Attempts have been made to use R. maximum in American nurseries, because of the tenderness of R. ponticum, but no great progress has been made. It is asserted that the rat growth is somewhat slower than that of the hybrids; this seems hardly possible, and it is to be hoped that further experiments will be made.R.  should be established in pots in spring and grafted under glass in autumn and early winter, using the veneer-graft (see Grafting, page 1362, Vol. III). Graft as near the root as possible ancf plant the worked parts below the surface when planting in the nursery or permanently. With these precautions, and an extra covering of leaves until the plant is established on its own roots, the defect of tenderness in this stock can be overcome. Nurse carefully the young grafted plants in frames until of sufficient size to be planted in the nursery rows. Figs. 3380 and 3381 illustrate two common methods of grafting rhododendrons and other woody plants. The details of the unions are shown in Fig. 3380, and the completed work in Fig. 3381. Statements are made that cuttings of half-ripened wood will strike, but it is not likely that this will ever prove a practical method of propagating R. maximum or the R. catawbiense hybrids; it might be worth while to experiment with wood grown under glass,particularly with some of the smaller-leaved evergreen kinds.

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 be removed when germination 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 clipping. Seed-pans or flats of convenient size are used and they should be plunged in sphagnum still further to insure even moisture; the temperature of the house should be 45° to 50° F. Seedlings are prone to damp-off and should be pricked 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 make 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 R. 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 Shrubs from Seeds," in Transactions of the Massachusetts Horticultural Society, 1885, part I, page 145.) Layers probably make the best plants, and in the best English nurseries layering is the common method of propagation. In the United States layering in spring is preferable, but abroad it is practised in both spring and autumn. It is a slow process, but desirable for the hardy hybrids of R. catawbiense. Roots form on wood of almost any age; when removed the layers should be treated as rooted cuttings and carefully grown in well-prepared soil where water and shade are easily furnished. See Layering. See, also, G.F. 6:63 (1893) for an interesting account of layering large plants by burying them to the top.-Grafting is the common method of propagation, and is employed almost universally in continental nurseries. R. ponticum is the usual stock, a free grower and readily obtained from seeds. Attempts have been made to use R. maximum in American nurseries, because of the tenderness of R. ponticum, but no great progress has been made. It is asserted that the rat growth is somewhat slower than that of the hybrids; this seems hardly possible, and it is to be hoped that further experiments will be made.R.  should be established in pots in spring and grafted under glass in autumn and early winter, using the veneer-graft (see Grafting, page 1362, Vol. III). Graft as near the root as possible ancf plant the worked parts below the surface when planting in the nursery or permanently. With these precautions, and an extra covering of leaves until the plant is established on its own roots, the defect of tenderness in this stock can be overcome. Nurse carefully the young grafted plants in frames until of sufficient size to be planted in the nursery rows. Figs. 3380 and 3381 illustrate two common methods of grafting rhododendrons and other woody plants. The details of the unions are shown in Fig. 3380, and the completed work in Fig. 3381. Statements are made that cuttings of half-ripened wood will strike, but it is not likely that this will ever prove a practical method of propagating R. maximum or the R. catawbiense hybrids; it might be worth while to experiment with wood grown under glass,particularly with some of the smaller-leaved evergreen kinds.

As to cultivation, the point on which successful American growers of rhododendrons now insist is that the water-supply shall be sufficient. (See H. H. Hun- newell, in G.K 3:201, 1890.) To effect this: (1) make the soil deep and fine, using materials like peat, leaf- mold, well-rotted manure and yellow loam, all of which are retentive of moisture; (2) plant in masses, at any rate while young, so that they may protect each other and prevent evaporation; (3) give the bed a northern exposure or a situation where the force of the midday sun is broken; (4) do not plant under or near trees like elm, oak, or maple, which make undue inroads on the natural water-supply, nor so near buildings that the border is sheltered from rain or overdrained by cellar walls; (5) mulch with leaves summer and winter, protect from wind and sun with evergreen boughs in winter and in summer give heavy watering whenever the weather is excessively hot or dry.

As to cultivation, the point on which successful American growers of rhododendrons now insist is that the water-supply shall be sufficient. (See H. H. Hun- newell, in G.K 3:201, 1890.) To effect this: (1) make the soil deep and fine, using materials like peat, leaf- mold, well-rotted manure and yellow loam, all of which are retentive of moisture; (2) plant in masses, at any rate while young, so that they may protect each other and prevent evaporation; (3) give the bed a northern exposure or a situation where the force of the midday sun is broken; (4) do not plant under or near trees like elm, oak, or maple, which make undue inroads on the natural water-supply, nor so near buildings that the border is sheltered from rain or overdrained by cellar walls; (5) mulch with leaves summer and winter, protect from wind and sun with evergreen boughs in winter and in summer give heavy watering whenever the weather is excessively hot or dry.

The following species and hybrids are hardy: R. arbutifolium, campanulatum, caucasicum pictum, carolinianum, dahuricum, ferru- gincum, hirsutum, Metternichii, mucronulatum, myrtifolium, Smir- novii.

The following species and hybrids are hardy: R. arbutifolium, campanulatum, caucasicum pictum, carolinianum, dahuricum, ferru- gincum, hirsutum, Metternichii, mucronulatum, myrtifolium, Smir- novii.

Hatdy deciduous azaleas.

Hardy deciduous azaleas.

These include the species of the sections Pentathera and Rhodora and some of the section Tsutsutsi, and the hybrids known as Ghent azaleas. Most of them are hardy, but in the North and in exposed situations a protection with brush, hay, or mats should be given in winter, to protect the flower buds from sudden changes of temperature.

These include the species of the sections Pentathera and Rhodora and some of the section Tsutsutsi, and the hybrids known as Ghent azaleas. Most of them are hardy, but in the North and in exposed situations a protection with brush, hay, or mats should be given in winter, to protect the flower buds from sudden changes of temperature.

Double-flowered varieties: Arethusa, Bijou de Gand-brugge (F.S. 19:2024); Louis Aime Van Houtte (F.S. 19:2022); Madame Mina Van Houtte (F.S. 19:2021); Murillo (R.B. 19:232); Phebe (R.B. 19:232); Raphael de Smet, Virgile (R.B. 19:232. G.W. 15, p. 493).

Double-flowered varieties: Arethusa, Bijou de Gand-brugge (F.S. 19:2024); Louis Aime Van Houtte (F.S. 19:2022); Madame Mina Van Houtte (F.S. 19:2021); Murillo (R.B. 19:232); Phebe (R.B. 19:232); Raphael de Smet, Virgile (R.B. 19:232. G.W. 15, p. 493).

Indian azaleas.

Indian azaleas.

This group contains R. indicum and other species of the section Tsutsutsi and the hybrids of them. They are well-known evergreen shrubs, in the North requiring cultivation in the greenhouse during the winter, but some, as R. Kaempferi and R. poukhanense, have proved perfectly hardy in the neighborhood of Boston; also R. ledifolium and R. linearifolium will stand many degrees of frost in somewhat sheltered positions. Indian azaleas are rarely increased by seeds, which may be sown in the greenhouse in the same way as with the former group. Usually they are propagated by cuttings or grafting. The cuttings root best when made in August from half-ripened wood, and placed in sand under a frame, with gentle bottom heat. Choicer varieties are usually increased by veneer- or tongue-grafting, either in winter or in July and August on vigorous-growing varieties raised mostly from cuttings. Grafting on rhododendron is now used in some German nurseries with very good results. The best soil for azaleas, if grown in pots, is a sandy compost of half peat and half leaf-soil, with an addition of good fibrous loam. It is essential to plant them firmly, and to give very good drainage. The base of the stem should be just above the surface. The best time for repotting is after flowering, when the new growth commences. During the summer, they should be kept in a coldframe or in the open in a sheltered spot, with the pots plunged in the soil, or planted out in prepared beds, where they make a very vigorous and healthy growth. In September they should be repotted and transferred to the greenhouse. They must have plenty of water and free syringing during the hot months. The natural flowering time is from April to June, but in the greenhouse, azaleas may be had in flower from November till June. Against the red-spider and thrips, from which the azaleas are liable to suffer if the air is too dry, free syringing with water is the best remedy. Most of the plants used for forcing in this country are imported from Holland, Belgium, and Germany. Formerly azaleas were kept in summer in shade or partial shade, but now it is the custom of the best growers to give them full exposure to the sun, either planted out or in the pots plunged to the rim in ashes or other good drainage material; in the latter case a top-dressing of 2 or 3 inches of old cow-manure is very beneficial. The only American treatise is Halliday's "Treatise on the Propagation and Cultivation of Azalea Indica," Baltimore, 1880.

This group contains R. indicum and other species of the section Tsutsutsi and the hybrids of them. They are well-known evergreen shrubs, in the North requiring cultivation in the greenhouse during the winter, but some, as R. Kaempferi and R. poukhanense, have proved perfectly hardy in the neighborhood of Boston; also R. ledifolium and R. linearifolium will stand many degrees of frost in somewhat sheltered positions. Indian azaleas are rarely increased by seeds, which may be sown in the greenhouse in the same way as with the former group. Usually they are propagated by cuttings or grafting. The cuttings root best when made in August from half-ripened wood, and placed in sand under a frame, with gentle bottom heat. Choicer varieties are usually increased by veneer- or tongue-grafting, either in winter or in July and August on vigorous-growing varieties raised mostly from cuttings. Grafting on rhododendron is now used in some German nurseries with very good results. The best soil for azaleas, if grown in pots, is a sandy compost of half peat and half leaf-soil, with an addition of good fibrous loam. It is essential to plant them firmly, and to give very good drainage. The base of the stem should be just above the surface. The best time for repotting is after flowering, when the new growth commences. During the summer, they should be kept in a coldframe or in the open in a sheltered spot, with the pots plunged in the soil, or planted out in prepared beds, where they make a very vigorous and healthy growth. In September they should be repotted and transferred to the greenhouse. They must have plenty of water and free syringing during the hot months. The natural flowering time is from April to June, but in the greenhouse, azaleas may be had in flower from November till June. Against the red-spider and thrips, from which the azaleas are liable to suffer if the air is too dry, free syringing with water is the best remedy. Most of the plants used for forcing in this country are imported from Holland, Belgium, and Germany. Formerly azaleas were kept in summer in shade or partial shade, but now it is the custom of the best growers to give them full exposure to the sun, either planted out or in the pots plunged to the rim in ashes or other good drainage material; in the latter case a top-dressing of 2 or 3 inches of old cow-manure is very beneficial. The only American treatise is Halliday's "Treatise on the Propagation and Cultivation of Azalea Indica," Baltimore, 1880.

Plants grown in Germany are preferred for early forcing, because they are grown in pots over summer before shipping, while the Belgian plants are grown in the open field. Generally the Belgian plants are grown more compact, while the German-grown plants are of looser, more naturally graceful habit. Some varieties, though much approved abroad, are rarely imported. because they do not travel well.

Plants grown in Germany are preferred for early forcing, because they are grown in pots over summer before shipping, while the Belgian plants are grown in the open field. Generally the Belgian plants are grown more compact, while the German-grown plants are of looser, more naturally graceful habit. Some varieties, though much approved abroad, are rarely imported. because they do not travel well.

Index.

*Subgenus ''[[Rhododendron subgenus Therorhodion|Therorhodion]]'': one species, ''[[Rhododendron camtschaticum]]''.  

(Including the specific names under Azalea.)

 

 

 

 

 

 

 

(Including the specific names under Azalea.)

aeruginosum, 22. flavidum, 19 and obtusum, 48.

aeruginosum, 22. flavidum, 19 and obtusum, 48.

croceum, 35. suppl. washingtoniainum, 25. Cuthbertii, 6. narcissiflorum, 44. Wilsonii, 4 and suppl. dahuricum, 14, 15. nilagiricum, 17. Windsorii, 17. Danielsianum, 45. nitidum, 32. yanthinum, 11. daphnoides, 4. Noordtianum, 44. yodogawa, 43. ferrugineum, 2. nudiflorum, 33. yunnanense, 10.

croceum, 35. suppl. washingtoniainum, 25. Cuthbertii, 6. narcissiflorum, 44. Wilsonii, 4 and suppl. dahuricum, 14, 15. nilagiricum, 17. Windsorii, 17. Danielsianum, 45. nitidum, 32. yanthinum, 11. daphnoides, 4. Noordtianum, 44. yodogawa, 43. ferrugineum, 2. nudiflorum, 33. yunnanense, 10.

}}

}}

==Gallery==

| name = ''Rhododendron''

| image = rhododendron-by-eiffel-public-domain-20040617.jpg

image:Pink Rhododendron.jpg

| image_width = 250px

File:Rhododendron decorum ssp diaprepes -1.jpg|''Rhododendron decorum'' subsp. ''diaprepes''

| image_caption = ''Rhododendron ponticum''

File:rhododendron2.jpg

File:Wild Rhododendrons in Kashmir.jpg|Wild Rhododendrons in Kashmir by [[Edward Molyneux]]; painted before 1908

File:Rhododendron 1 Fcb981.JPG

File:Wild Rhododendrons in Whitwick Leicestershire 1155.JPG | Flowering Rhododendrons in Whitwick Leicestershire

File:Rhododendron luteum (flower).jpg|Rhododendron luteum

File:Sorakuen16st3200.jpg|Rhododendrons in Sōrakuen garden, [[Kobe]]

</gallery>

Source: [http://www.rbge.org.uk RBG, Edinburgh]

 

'''''Rhododendron''''' (from the [[Greek language|Greek]]: ''rhodos'', "rose", and ''dendron'', "tree") is a genus of flowering plants in the family [[Ericaceae]]. It is a large genus with over 1000 [[species]] and most have showy flower displays. It includes the plants known to gardeners as [[azalea]]s. It's the [[national flower]] of [[Nepal]].

 

The Rhododendron is a genus characterized by [[shrub]]s and small to (rarely) large [[tree]]s, the smallest species growing to 10-100 cm tall, and the largest, ''R. giganteum'', reported to over 30 m tall<ref>[http://wildeel.com/rhodotree.html Tree rhododendrons]</ref>. The [[leaf|leaves]] are spirally arranged; leaf size can range from 1-2 cm to over 50 cm, exceptionally 100 cm in ''R. sinogrande''. They may be either [[evergreen]] or [[deciduous]]. In some species the underside of the leaves is covered with scales (lepidote) or hairs (indumentum).  Some of the best known species are noted for their many clusters of large flowers. There are alpine species with small flowers and small leaves, and tropical species such as section ''Vireya'' that often grow as [[epiphyte]]s.

 

'''Rhododendron''' is a very widely distributed genus, occurring throughout most of the [[Northern Hemisphere]] except for dry areas, and extending into the [[Southern Hemisphere]] in southeastern [[Asia]] and northern [[Australasia]]. The highest species diversity is found in the [[Himalaya]]n mountains from [[Uttarakhand]], [[Nepal]] and [[Sikkim]] to [[Yunnan]] and [[Sichuan]], with other significant areas of diversity in the mountains of [[Indo-China]], [[Korea]], [[Japan]] and [[Taiwan]]. Rhododendron, also known as "Lali Guras" in local language is the national flower of [[Nepal]] and the state tree of the state of [[Uttarakhand]] in [[India]]. In Korea, [[Rhododendron schlippenbachii]] is particularly common (called 철쭉(choltjuk)). In addition, there are a significant number of tropical rhododendron species from southeast Asia to northern [[Australia]], with 55 known species in [[Borneo]] and 164 in [[New Guinea]]. <ref name="Argent 2006">Argent, G. ''Rhododendrons of subgenus Vireya''. 2006. Royal Horticultural Society. ISBN 1-902896-61-0</ref> Relatively fewer species occur in [[North America]] and [[Europe]].  Rhododendrons have not been found in South America or Africa.

 

[[Image:Rhododendron wardii var puralbum.jpg|thumb|250px|right|''Rhododendron wardii var. puralbum'']]

The species are organized by subgenus, section, subsection and series. These are currently divided into four large and four small subgenera:

*Subgenus ''Rhododendron'' L.: small leaf or lepidotes (with scales on the underside of their leaves); several hundred species, type: ''[[Rhododendron ferrugineum]]''. The tropical rhododendrons (sect. ''Vireya'', about 300 species) are usually included as a section in this subgenus, but sometimes split off as a ninth subgenus.]]''.  

 

Recent genetic investigations have caused an ongoing realignment of species and groups within the genus, and also have caused the old genus ''[[Ledum]]'' to be reclassified within subgenus ''Rhododendron''. Further realignment within the subgenera is currently proposed <ref name="Goetsch et al.">Goetsch, L. A., Eckert, A. J. & Hall, B. D. (2005). [http://www.ingentaconnect.com/content/aspt/sb/2005/00000030/00000003/art00012 The molecular systematics of Rhododendron (Ericaceae): A Phylogeny based upon RPB2 gene sequences]. ''Sys. Bot''. 30(3): 616-626.</ref><ref>[http://www.flounder.ca/FraserSouth/Goetsch-Eckert-Hall.asp Summary of Goetsch-Eckert-Hall results]</ref>, including the merging of subgenus ''Hymenanthes'' into subgenus ''Pentanthera''.

 

Rhododendrons are extensively hybridized in cultivation, and natural hybrids often occur in areas where species ranges overlap. There are over 28,000 [[cultivar]]s of Rhododendron in the [http://www.rhs.org.uk/plants/registration_rhododendron.asp International Rhododendron Registry] held by the [[Royal Horticultural Society]]. Most have been bred for their flowers, but a few are of garden interest because of ornamental leaves and some for ornamental bark or stems.

 

Some species (e.g. ''[[Rhododendron ponticum]]'' in the [[United Kingdom]]) are invasive as introduced plants, spreading in woodland areas replacing the natural understory. R. ponticum is difficult to eradicate, as its roots can make new shoots.  

 

[[Image:Garden with Rhododendrons.JPG|500px|thumb|right|| A garden with tall Rhododendrons in Lynnwood, Washington]]

 

;Sample species:

*''[[Rhododendron luteum]]''

 

*[[Rhododendron 'President Roosevelt'|''Rhododendron'' 'President Roosevelt']]

 

<!-- Image with unknown copyright status removed: [[Image:Bee Collecting Pollen From Rhododendron.JPG|500px|thumb|right|| A Bee Collecting Pollen from a Rhododendron Flower]] -->

 

Some species are poisonous to grazing animals. These Rhododendrons have a [[toxin]] called [[grayanotoxin]] in their [[pollen]] and [[nectar (plant)|nectar]]. People have been known to become ill from eating [[honey]] made by [[bee]]s feeding on rhododendron and azalea flowers. Rhododendron is extremely toxic to horses, with some animals dying within a few hours of ingesting the plant, although most horses tend to avoid it if they have access to good forage.

 

Like other [[Ericaceae|ericaceous]] plants, most rhododendrons prefer acid soils with a pH of roughly 4.5-5.5; some tropical Vireyas and a few other rhododendron species grow as [[epiphyte]]s and require a planting mix similar to [[orchids]].  Rhododendrons have fibrous roots and prefer well-drained soils high in organic material.  In areas with poorly-drained or alkaline soils, rhododendrons are often grown in raised beds using mediums such as composted pine bark.<ref>[http://www.rhododendron.org/soil.htm Soil information for planting rhododendrons]</ref> Mulching and careful watering are important, especially before the plant is established.

 

 

 

 

 

 

==References==

==References==

*Cox, P. A. & Kenneth, N. E. ''The Encyclopedia of Rhododendron Species''. 1997. Glendoick Publishing. ISBN 0-9530533-0-X.

*[[Standard Cyclopedia of Horticulture]], by L. H. Bailey, MacMillan Co., 1963

*Davidian, H. H. ''The Rhododendron Species''. In four volumes from 1982-1995. Timber Press. ISBN 0-917304-71-3, ISBN 0-88192-109-2, ISBN 0-88192-168-8, ISBN 0-88192-311-7.

<!--- xxxxx  *Flora: The Gardener's Bible, by Sean Hogan. Global Book Publishing, 2003. ISBN 0881925381  -->

 

<!--- xxxxx  *American Horticultural Society: A-Z Encyclopedia of Garden Plants, by Christopher Brickell, Judith D. Zuk. 1996. ISBN 0789419432  -->

<!--- xxxxx  *Sunset National Garden Book. Sunset Books, Inc., 1997. ISBN 0376038608  -->

==External links==

==External links==

* [http://en.wikipedia.org/wiki/Rhododendron Wikipedia article]

*{{wplink}}