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Rhododendron: The Hybrids / Azalea Hybrids - Deciduous

Family

These azaleas all derive from species of the subseries Luteum of the Azalea series, which in modern classifications ranks as a subgenus of Rhododendron (subg. Azalea, also known as subg. Pentanthera). Of the component species all are American except R. luteum, the Pontic azalea, and two closely allied species from E. Asia, R. molle and R. japonicum. The hybrids that have resulted from the mingling of these are all that garden shrubs should be – hardy, undemanding, sun-tolerant, and colourful. Mostly the flowers are fragrant (except in the Mollis azaleas) and in many of them the leaves colour well before they fall. The season of the deciduous azaleas starts early in May with the Mollis hybrids and lasts until about the third week in June, when the later Ghents and Knap Hills are in flower.

Ghent Azaleas

The Ghents are the oldest of the hybrid deciduous azaleas and could be regarded as the counterpart of the earliest hybrid rhododendrons, which derive from R. maximum, R. catawbiense, and R. ponticum. Like these they are the result of crossing species of eastern North America with their one European relative, in this case the Pontic azalea, R. luteum, and therefore owe nothing to the Himalaya nor to Eastern Asia. Which American species were used is not known, but R. calendulaceum, R. periclymenoides, and R. viscosum were certainly among them. Some may be purely American in parentage, especially the later flowering sorts. It is probable that most of the present commercial stock derives from the crosses made by the Belgian baker P. Mortier of Ghent in the 1820s and 1830s, which soon entered the trade and had reached Britain by 1831. In his 1836 catalogue, Loddiges of Hackney listed seventy-two ‘Hybridae Belgicae’, among them two still cultivated today – ‘Gloria Mundi’ and the well-known ‘Coccinea Speciosa’. Ghent-type crosses were also made at Highclere by Gowen for the Earl of Carnarvon, and of these Loddiges offered twenty-four, but none of the names appears in any modern list. It is also said that Ghents were raised in some British nurseries early in the last century, which may be so. But a list of those cultivated in the Knap Hill Nursery in 1852 contains seven names – a third of the total – that also occur among the Belgian hybrids offered by Loddiges, and not one that suggests an English origin.

Despite the large number of Ghents that were raised and named in the last century, a search through the horticultural literature of the Victorian period provides no confirmation for the statement often made that they were popular garden plants at that time. On the contrary, writers in the 1870s refer to them as uncommon. Millais, writing almost half-a-century later (1917), made the same observation. At the present time they are quite overshadowed by the large-flowered modern hybrids. This is a pity, for the Ghent azaleas are valuable garden plants, strong-growing and trouble-free, and mostly giving vivid autumn colour. Their small flowers render them more suitable for natural plantings than the large-flowered hybrids.

An interesting character of the Ghent azaleas (and of later hybrids deriving from them) is that seedlings occasionally occur in which the stamens are converted into petals. Since the stamens are always five in number and alternate with the corolla-lobes, the result is a fairly symmetrical ‘hose-in-hose’ flower. The best known of these double Ghents is ‘Narcissiflora’. There is another group with double flowers of similar form known as Rustica Flore Pleno. These were put into commerce by Charles Vuylsteke of Loochristi, near Ghent, in 1888, and are usually supposed to be the result of crossing double Ghents with Mollis azaleas. Like the Mollis azaleas they were intended primarily for forcing, and had the advantage that their flowers lasted longer. The best known of this group is ‘Norma’.

Mollis (Mollis-Sinensis) Azaleas

The Mollis azaleas, as they are usually called, derive mainly from R. iaponicum, the only Japanese member of the Luteum subseries, which in the last century was generally known as Azalea mollis, but its Chinese relative, then known as Azalea sinensis, enters into the parentage of some varieties, As pointed out in the section on the species, the name Azalea mollis was wrongly used, for it belonged properly to the Chinese azalea, which therefore takes the name R. molle (Bl.) Wils., while the Japanese species (the Azalea mollis of 19th-century gardens) becomes R. japonicum. The purist should therefore call the group the Japonicum or Japonicum-Molle azaleas, but the traditional nomenclature is accepted by the International Register. It is in any case erroneous to refer to these azaleas as × Molle hybrids, as is sometimes done, since this implies that R. molle (the former Azalea sinensis of gardens) is the dominant parent, which is certainly not the case.

The Mollis group owes its origin to the great Belgian nurseryman Louis van Houtte, who had named some twenty varieties by 1873. It is usually said that he obtained his stock from Siebold’s nursery at Leyden in Holland, which had obtained R. japonicum (Azalea mollis) from Japan in 1861. It seems to have been overlooked that van Houtte stated that his new azaleas were the result of thirty years of breeding, which, if true, means that their origin goes back to the early 1840s and that according to some authorities R. japonicum was introduced by Siebold in 1830. The wide colour-range of the twenty original varieties certainly suggests a long period of breeding. R. japonicum commonly bears orange-red or flame-red flowers in the wild, rarely yellow. The van Houtte varieties ranged in colour from lemon- and buff-yellow through rose and salmon to orange and salmon-red. Furthermore, the beautiful ‘Chevalier de Reali’ has very fragrant flowers, whereas those of R. japonicum are almost scentless. It is also of possible significance that van Houtte had an azalea, called by him Azalea sinensis alba, which, as Rehder suggested, seems to be a hybrid between R. molle and R. viscosum. The pale yellow varieties put out by van Houtte may well have derived from this, and possibly some of the others.

By the late 1870s the Mollis azaleas had become important commercial plants but, like most of the azaleas grown in the last century, they were looked on primarily as subjects for the decoration of house or conservatory, bought or lifted from the reserve border, in early winter, potted up and forced into flower. ‘Those who have not seen the thousands – the acres – of these plants in the grounds at Gendbrugge can form no conception of the magnitude of the trade in them – trade which extends to all the nations of the civilised world’ (Journ. Hort., Vol. 33 (1877), p. 449).

The group was soon taken up and further developed by the Dutch nurserymen, and it was also a Dutch firm – M. Koster and Sons – who first put into commerce varieties that are known to have been the result of crossing R. japonicum with R. molle, though, as just pointed out, there is a distinct possibility that the original van Houtte varieties had ‘Chinese’ blood in them. The Koster varieties, which were actually raised by another Dutch grower, were first put into commerce in 1892, and many others followed before the end of the century. Other Dutch breeders also used the Chinese as well as the Japanese azalea, but there has been so much intercrossing between the varieties that it is now no longer possible to differentiate between those that are colour-forms of R. japonicum and those that are in some degree hybrid in origin (H. J. Grootendorst, Rhododendron en Azaleas (1954), pp. 112-18).

In the work just cited, Mr Grootendorst gives interesting information concerning the propagation of Mollis azaleas by seeds. Of the varieties described here, ‘Babeuff’ (the original clone only) comes fairly true from seed when isolated. ‘J. C. van Tol’ is a hybrid between a red and yellow form, and throws three-quarters red and one-quarter yellow when selfed. Of these, the yellows breed true but are poor growers; the reds in the second generation give one-third true-breeding reds, while the other two-thirds resemble the original ‘J. C. van Tol’ in their genetic make-up. These are the Mendelian ratios to be expected when red is dominant over yellow. In the course of their breeding, M. Koster and Sons discovered that if certain selected Mollis azaleas are crossed, the progeny is more or less uniform in colour, and it is therefore possible, by repeating the cross annually, to produce quantities of seedling azaleas true to colour. The first Mollis azalea to be propagated in this way was ‘Koster’s Brilliant Red’, which was therefore not originally a clone. But some of the seedlings have since been propagated vegetatively, so that the name now covers several similar but not identical clones. Other Dutch nurseries now produce such line-hybrids, but the seedlings are usually sold to colour, without a distinguishing cultivar name.

Although the Mollis azaleas were originally sent out as plants for forcing, they were being grown in the open ground at Kew by the end of the 19th century and are now little used for their original purpose. Since the second world war they have had to compete with the Knap Hill and Exbury azaleas, but are still widely grown and well represented in commerce. For the most part their flowering time is in the first half of May, which means that their display is at risk in frosty gardens, but that, and their lack of fragrance, are their only faults. They are very hardy, of good habit, and do not grow much over 4 or 5 ft high. Full sun is best for them but they will stand slight shade. The most characteristic colours in this group are in the orange, flame, and red part of the spectrum, and at their best are of a truly remarkable brilliance.

Knap hill Azaleas

The Ghent azaleas are the result of crossing the small-flowered, long-tubed species of eastern North America with their European relative. The Mollis azaleas unite the two larger flowered, short-tubed species of eastern Asia. The Knap Hill azaleas, as usually defined, are an omnium gatherum of hybrids that derive from both the Pontic-American and the east Asiatic species and also have another character in common, namely that they all have in their ancestry azaleas bred in the Knap Hill Nursery in the time of the two Anthony Waterers, father and son, who are therefore the founders of the group, though few of the clones now in commerce were actually raised by them.

The history of the Knap Hill group goes back to the middle of the last century, when Anthony Waterer and his partner set out to improve the Ghents by crossing them with the Chinese azalea R. molle, formerly known as Azalea sinensis. In 1861 the GardenersChronicle reported: ‘Some fine seedlings have been obtained, with blooms of large size and possessing great richness and variety of colour. They also have the good property of being late bloomers. Though among them orange and flame-coloured tints prevail, yet one we remarked had a crimson top petal and the rest rose; equally remarkable combinations of colour were also to be met with in other sorts’ (Gard. Chron. (1861), p. 531).

By the end of the century there were seedlings with flowers over 3 in. across, but none of these ‘improved Ghents’ was ever named and propagated, with the exception of ‘Nancy Waterer’, which is usually classified as an ordinary Ghent. A possible reason for this neglect is that from the early 1870s the British market was flooded with the Belgian and later the Dutch Mollis hybrids, which had flowers quite as large and vividly coloured as the Waterer azaleas and fulfilled the prevailing demand for ‘forcing’ plants. At that time, there seems to have been little demand for Ghents, improved or otherwise. Taste began to change early in this century, and the merits of the deciduous azaleas as garden plants began to be appreciated. The Knap Hill Ghents were now in demand, but the plants sent out were seedlings. The younger Anthony Waterer, who succeeded in 1896, carried on his father’s work but, being of ample means and somewhat eccentric, he never bothered to exploit it commercially. The best of the Knap Hill azaleas never left the nursery in his lifetime, and the gardening public at large had no notion of what he and his father had achieved. ‘The colours have always been remarkable: the crimson deep and solid, the scarlets brilliant as a new hunting coat, the yellows attaining the colour of rich Guernsey butter, the oranges bright with crimson filaments to the anthers, and of course there were beautiful pinks and whites’ (Rhodo. Soc. Notes, Vol. II, p. 274). So wrote P. D. Williams of Lanarth after the younger Anthony’s death in 1924. He and his cousin J. C. Williams of Caerhays were favourites of Anthony Waterer and received some of his prized seedlings. Lionel de Rothschild also acquired some before 1924, but the Knap Hill azaleas did not reach the trade until 1930, when much of the stock was sold to other nurserymen, and many years passed before any became available to the public. Since the second world war, the Knap Hill Nursery has resumed hybridising and put out many new varieties, and other growers have also developed the Knap Hill breed.

The Exbury strain of the Knap Hill azaleas demands special mention, since it has developed to the stage where it is surely entitled to independent rank. About 1921 Lionel de Rothschild acquired from Anthony Waterer an azalea named ‘George Reynolds’ which had butter-yellow flowers of very large size. Curiously enough, it is very uncharacteristic of the Knap Hill breed, being nearer to a Mollis-Sinensis hybrid than to a Ghent, which may explain why Anthony Waterer was willing to part with it. This was crossed at Exbury with some unnamed Knap Hill azaleas with orange flowers, and one of the seedlings from this cross received an Award of Merit in 1934 under the name ‘Hotspur’. A few years after Anthony Waterer’s death, Lionel de Rothschild acquired a financial interest in the Knap Hill Nursery and was therefore in a position to draw on its resources. He also used true R. molle, raised from seeds collected in China by Forrest and by Rock. Discarding all but the best seedlings, and crossing only within the various colour-groups, he produced a splendid strain that owes as much to his efficiency and sound judgement as it does to the work of the Anthony Waterers. It is doubtful whether any Boskoop nurseryman, breeding for a competitive market, could have achieved as much as this amateur did in such a short space of time. Further details concerning the Exbury azaleas will be found in The Rothschild Rhododendrons, pp. 36-7 and plates 39-48. Many Exbury clones have been named and received awards, but the greater part of those in cultivation are seedlings supplied to colour, of which large quantities have been exported to the United States.

The Knap Hill group of azaleas are mostly of moderate growth, to about 5 ft. The young foliage in many clones and seedlings is bronze-tinted, and many also give excellent autumn colour. The flowers are more or less fragrant, larger than in the Ghents, sometimes much larger, and the tube of the corolla is generally longer than it is in the Mollis type of azalea. The influence of R. molle is often shown by a flare of discrete markings, while others have the solid flare characteristic of the Ghents. The group as a whole, including the Exbury strain, is a very large one and is open-ended, for new sorts are being named all the time. Here it is possible to mention only those that have received awards and are available from more than one nurseryman. It should also be mentioned that in this group seedlings are available in the trade, sold to colour, which are often only marginally inferior to named clones.

Occidentale Hybrids

R. occidentale is closely related to the East American members of the Luteum subseries, having the white flowers of R. viscosum but in other respects being near to R. calendulaceum. But being a native of western North America it was introduced later – around 1851 by William Lobb for Messrs Veitch. This was apparently a poor form (the species is very variable). However, the elder Anthony Waterer, probably through his American friends, introduced a finer form in the 1870s, for which he received a Botanical Certificate in 1886. Being very late-flowering it had potentialities as a parent and was crossed at Knap Hill with Ghent azaleas, presumably of the improved type then being bred there. By 1890, there were numerous seedlings of this new race in the nursery, with flowers ranging from white through cream to pink and deep pink, fragrant, with unusually long tubes. They flowered very late – some at the end of June and in early July. These azaleas went into commerce, but those known to Millais (1917) were mainly white, and ranged in flowering time from June 1 to July 15. These were seedlings. Apparently no named clones were distributed, but ‘Mrs Anthony Waterer’ (F.C.C. 1892) should probably be regarded as one of these Occidentale hybrids, rather than as a member of the Knap Hill group. It may be that the two groups were interbred in the time of the younger Anthony Waterer, for some of the white-flowered Knap Hill and Exbury azaleas seem to have R. occidentale blood in them. ‘Albicans’, also raised at Knap Hill, was said to be a hybrid between R. occidentale and R. molle. It received an Award of Merit in 1894 when shown from Syon House, but seems to have been lost.

The Occidentale hybrids now in commerce consist mainly of a group of rather similar clones raised by M. Koster and Sons of Holland by crossing R. occidentale with Mollis-Sinensis azaleas in 1895. See ‘Delicatissima’, Exquisita’, ‘Graciosa’, and ‘Superba’. All are lovely, with delicately coloured fragrant flowers, borne in late May or early June, and growing to 5 or 6 ft high, but are best kept away from more brightly coloured azaleas. See also ‘Bridesmaid’ and ‘Irene Koster’.

DESCRIPTIONS

‘Adriaan Koster’. – Deep pure yellow (Mollis; M. Koster and Sons, 1901). One of the few self-coloured yellows in the Mollis group, and probably the best.

‘Albatross’. – White with a pink tinge on the reverse, wavy at the margin (Knap Hill, 1941). A.M.T. May 26, 1953.

‘Alice de Stuers’. – Salmon-pink suffused with orange-pink; flare orange (Mollis; M. Koster and Sons). A.M.T. May 11, 1959.

‘Altaclarense’. – This name belongs properly to a hybrid between R. molle (Azalea sinensis) and a late flowering form of R. viscosum, raised at Highclere and figured in Bot. Reg. (1842), t. 27. It had white flowers, flushed with pink at the edge, spotted with yellow on the upper lobe and with a tinge of yellow in the throat. It must have been similar to ‘Daviesii’ (q.v.), which has the same parentage. The azalea grown at the present time as ‘Altaclarense’ is quite different and evidently not of the same parentage. The flowers are soft yellow with a deeper flare, and with an orange-pink flush on the upper lobes which fades as the flower ages. It received a First Class Certificate in 1862, when shown by Lee of Hammersmith, and was said to be Azalea sinensis × Ghent azalea. An excellent azalea, giving good autumn colour. It does not fall into any established category, but in appearance and flowering time it is nearer to the Mollis azaleas than to the Ghents, with which it is grouped in the International Register.

‘Altaclarense’ is said to be the same as ‘Aurea Grandiflora’, of which the nurseryman William Young of Milford held the entire stock in 1859 (Gard. Chron. (1859), p. 891). The parentage of this was stated by Young to be Azalea sinensis × Azalea pontica (i.e., R. molle × R. luteum).

For ‘Altaclarense Sunbeam’ see ‘Sunbeam’. For azaleas deriving from ‘Altaclarense’ see ‘Mrs Oliver Slocock’ and ‘Christopher Wren’. Another, apparently not yet in commerce in Britain, is ‘Golden Flare’, raised in Holland and highly rated there.

‘Amber Rain’. – Buttercup-yellow with an orange flare (Knap Hill – Exbury). A.M. May 19, 1958.

‘Annabella’. – Golden yellow flushed orange-rose (Knap Hill-Exbury, 1941).

‘Apple Blossom’. – Pure soft rose (Mollis; K. Wezelenburg and Son). Highly rated in the Boskoop Trials of 1966.

‘Babeuff’. – Apricot with an orange flare. Compact erect habit (Mollis; Gebr. Kersbergen, 1918).

‘Ballerina’. – White, very large, frilled at the edge, with a small, conspicuous orange flare (Knap Hill-Exbury).

‘Balzac’. – Deep orange with a darker, redder tube; flare flame-coloured (Knap Hill–Exbury). A.M. May 29, 1934 (Rothschild Rhododendrons, plate 43).

‘Basilisk’. – Deep yellow, flushed with salmon-pink outside and on the margins; lobes frilled; flare deep orange (Knap Hill-Exbury). A.M. May 29, 1934.

‘Berryrose’. – Salmon-pink with a tube of deep red; flare yellow (Knap Hill-Exbury). A.M. May 29, 1934.

‘Brazil’. – Bright tangerine; lobes frilled (Knap Hill-Exbury).

‘Bridesmaid’. – White with a yellow flare; buds pale greenish yellow. Leaves bright green. Dense habit (Occidentale Hybrid; Waterer, Bagshot).

‘Byron’. – Double, 2 in. wide, white, outer lobes tinged with Carmine Rose (Rustica fl.-pl.; C. Vuylsteke, 1888). A.M.T. May 11, 1953.

‘Cecile’. – Salmon-pink, darker pink in the bud, with a yellow flare (Knap Hill-Exbury). A beautiful azalea, recommended for an Award of Garden Merit.

‘Chevalier A. de Reali’. – Lemon-yellow in the bud, opening soft yellow, but the original colour retained for a time on the centre of each lobe; flare slightly darker yellow (Mollis; L. van Houtte, 1875).

‘Christopher Wren’. – Yellow, the two upper laterals flushed with orange pink; flare deep yellow (L. J. Endtz and Co.). A fine, vigorous azalea, believed to derive from ‘Altaclarense’. It flowers at the same time as the Mollis azaleas.

‘Coccinea Speciosa’. – Tangerine red, upper lobe yellower, 112 to 134 in. wide, tube slender, scarlet-crimson. A very old Ghent, listed by Loddiges in 1836, and still common in cultivation, recommended in 1968 for an Award of Garden Merit. It is of widely spreading habit and flowers in early June.

‘Corneille’. – Double, white flushed with pale pink, petaloids white, tube bright red at the base, its upper part and the outside of the limb pink (Ghent; C. Vuylsteke).

‘Coronation Lady’. – Salmon-pink with an orange-yellow flare (Knap Hill; Waterer, Bagshot). A fine azalea, raised from ‘Cecile’.

‘Daviesii’. – Buds buff-yellow, pink at the tips; open flowers 2 in. wide, at first creamy white flushed with pink, becoming pure white, slightly frilled, especially on the upper lobe; tube slender, it and the ribs of the limb covered with stalked glands. Leaves glaucous. Dwarf suckering habit. Late May or early June. An exquisitely beautiful azalea, raised by Isaac Davies of Ormskirk, Lancs, before 1879, from R. molle (Azalea sinensis) crossed with R. viscosum. Davies also raised ‘Avalanche’, of the same parentage, but with pure white flowers.

‘Daybreak’. – Orange-yellow suffused with bright red; flare orange (Knap Hill; Waterer, Bagshot). A.M.T. May 19, 1966.

‘Delicatissima’. – Soft yellow in the bud, opening cream with a slight tinge of pink, about 214 in. wide; flare yellow, not conspicuous. Fragrant (Occidentale Hybrid; M. Koster and Sons, 1901). ‘Magnifica’ is similar but less creamy.

‘Devon’. – Vivid blood-red, flushed with orange on the upper lobe, fragrant, 134 to 2 in. wide. Excellent autumn colour (Knap Hill; Slocock). A.M.T. May 22, 1952. ‘Satan’, raised at Knap Hill and distributed by Messrs Slocock, is similar.

‘Directeur Moerlands’ (‘Golden Sunlight’). – Golden yellow with a faint olive-brown flare (Mollis; raised in Holland).

‘Double Damask’. – Double, creamy white, fragrant (Knap Hill).

‘Dr M. Oosthoek’. – Deep orange-red, with a darker flare (Mollis; raised in Holland). A.M.T. May 20, 1940. The best of its colour, recommended for an Award of Garden Merit.

‘Eva Goude’. – Sulphur-yellow, almost self-coloured, fragrant (Knap Hill, 1951). Beautifully coloured, but a weak grower.

‘Exquisita’. – Creamy white, flushed with pink, especially on the upper lobes, flare orange, margins frilled. Fragrant (Occidentale Hybrid; M. Koster and Sons, 1901.) F.C.C.T. May 30, 1968.

‘Fanny’ (“Pucella”). – Deep purplish rose, 134 in. wide; tube red; flare orange. A Ghent azalea of unknown origin, very free-flowering in mid- or late May, of an unusual colour that clashes with most pinks and reds. The International Register gives ‘Pucella’ as its correct name – surely a corruption of ‘Pulchella’? It is possibly the same as ‘Pulchella Roseola’, described in the Register as ‘pinkish mauve, yellow blotch’.

‘Farall Yellow’. – Deep yellow with a flare of buttercup-yellow (Knap Hill; M. Haworth-Booth). A.M.T. 1957.

‘Floradora’. – Light orange with a flare of brownish spots (Mollis; M. Koster and Sons). A.M. 1911.

‘Frans van der Bom’. – Light apricot orange with darker markings on the upper lobe (Mollis; M. Koster and Sons, 1892).

‘Freya’. – Double, 112 in. wide, shell-pink tinged with deeper rosy pink (Rustica fl-pl.; Vuylsteke). A.M. 1897; A.M.T. May 11, 1953.

‘George Reynolds’. – Deep yellow, 312 in. wide, with a flare of orange spots. Raised at Knap Hill and acquired by Lionel de Rothschild, this is a parent of the famous Exbury strain of the Knap Hill azaleas. It received an Award of Merit when shown from Exbury on May 19, 1936. Rothschild Rhododendrons, plate 47.

‘Gibraltar’. – Rich orange-red, frilled, in a large truss (Knap Hill-Exbury, 1947).

‘Gog’. – Orange-red (Knap Hill, before 1927, distributed by Messrs Slocock). An azalea of exceptional vigour, colouring well in the autumn.

‘Goldcrest’. – Chrome-yellow with a flare of darker yellow, fragrant. Early (Knap Hill). A.M.T. May 11, 1953.

‘Golden Eye’. – Vermilion red with a large tangerine flare (Knap Hill). A.M.T. May 22, 1952.

‘Golden Oriole’. – Bright yellow with a darker flare, fragrant. Very vigorous and free-flowering. Early (Knap Hill).

‘Golden Sunset’. – Light yellow tinged with orange-red in the bud and when first expanded; flare orange (Knap Hill-Exbury, distributed by Waterer, Bagshot). A.M. May 22, 1956.

‘Graciosa’. – Soft yellow at first, becoming white, tinged with pink at the edge; large orange flare (Occidentale Hybrid; M. Koster and Sons). A.M. 1908.

‘Hamlet’. – Orange tinged with pink, with a darker flare (M. Koster and Sons). A.M.T. May 23, 1936. Although classed as a Mollis it flowers later than most members of that group.

‘Harvest Moon’. – Clear primrose-yellow with a slightly darker flare (Knap Hill; Slocock). A.M.T. May 26, 1953. A lovely azalea but not a strong grower. It associates well with the rhododendron ‘Purple Splendour’.

‘Homebush’. – Double, about sixteen in dense, rounded trusses, deep carmine-pink, about 112 in. wide. Raised at the Knap Hill Nursery before 1925 and distributed by Messrs Slocock. A charming azalea, similar to the Rustica Flore-pleno group. A.M.T. May 31, 1950. Numerous doubles, mostly with fragrant flowers, have been raised recently at Knap Hill by Donald Waterer, and were named in 1974.

‘Hortulanus H. Witte’. – Bright orange-yellow (Mollis; M. Koster and Sons).

‘Hotspur’. – Flame-red with a yellow flare, about 4 in. wide (Knap Hill-Exbury; ‘George Reynolds’ × Waterer’s orange seedling). A.M. May 29, 1934. Other seedlings were raised from this cross, similar in size and shape of flower, but of different colouring. Two of these, ‘Hotspur Orange’ and ‘Hotspur Red’, are sometimes sold as ‘Hotspur’ simply. Rothschild Rhododendrons, pp. 33-4, 105, plate 48.

‘Irene Koster’. – White, flushed crimson pink, but the central lobe almost white, with a yellow flare, 214 in. wide; tube crimson pink. Very fragrant (Occidentale Hybrid; Koster and Co.). According to H. J. Grootendorst, seedlings were originally distributed under this name.

‘J. C. van Tol’. – See p. 911.

‘Klondyke’. – Deep golden yellow, suffused salmon-red; buds orange and yellow (Knap Hill-Exbury, 1947).

‘Knap Hill Red’. – Brilliant red (Knap Hill, 1948).

‘Koster’s Brilliant Red’. – Bright orange-red (Mollis; M. Koster and Sons). Seedlings were originally sent out under this name, so there is some variation among the clones.

‘Lady Rosebery’. – Crimson with an orange flare, about 214 in. wide; trusses compact, with up to thirty flowers (Knap Hill, raised by Anthony Waterer II, introduced 1944).

‘Lapwing’. – Creamy yellow suffused with pink and with a deeper yellow flare, fragrant, 2 in. wide. Early (Knap Hill, 1935). A.M.T. May 11, 1953.

‘Marion Merriman’. – Chrome-yellow, flushed darker yellow, flare orange-yellow, six-lobed, truss with up to thirty flowers. (Knap Hill; raised by Anthony Waterer II and named the year after his death). A.M. 1925; A.M.T. May 31, 1950.

‘Mrs Anthony Waterer’. – Creamy white, about 2 in. wide, with a yellow flare and pink tube, very fragrant. Late. Good autumn colour. Raised at the Knap Hill Nursery, 1886. F.C.C. May 25, 1892. This is one of the elder Anthony Waterer’s hybrids of R. occidentale (see p. 914).

‘Mrs Oliver Slocock’. – Orange-yellow flushed terra-cotta. A hybrid between the yellow ‘Altaclarense’ and a Mollis azalea, raised by Messrs W. C. Slocock. A.M. May 9, 1933. A fine azalea, usually classified as a Mollis.

‘Mrs Peter Koster’. – Scarlet, with a flare of brownish orange (Mollis; M. Koster and Sons). A.M.T. May 11, 1953.

‘Nancy Waterer’. – Soft rich yellow, 2 in. wide, with a deeper flare (A. Waterer, Knap Hill; in commerce 1880). A beautiful, vigorous azalea, which received no award when it first appeared but has now been recommended for an Award of Garden Merit. It is usually classed as a Ghent, but is probably one of the first results of the elder Anthony Waterer’s attempts to improve the Ghents by crossing them with R. molle (Azalea sinensis).

‘Narcissiflora’ (‘Narcissiflora Plena’). – Flowers double, well formed, beautiful soft yellow, 112 in. wide, with a tube 1 in. long. Narrow habit. Bronze autumn colour. A fine azalea of unique colouring, excellent for the small garden. It is a Ghent, near to R. luteum, raised by L. van Houtte, before 1871. F.C.C. 1879. F.C.C.T. May 29, 1923,‘Bartholo Lazzari’Is similar but not so good.

‘Norma’. – Double, buff-pink, the upper lobe in some flowers marked with a slight orange flare; petaloids also buff-pink, but sometimes white with a yellow stain, both colours occurring in the same truss (Rustica fl.-pl.; Vuylsteke). A.M.T. 1959. In the year the award was given, the plant in the trials was flowering from May 9, but the usual flowering time for ‘Norma’ is mid- to late May. It is vigorous and very free-flowering.

‘Pallas’. – Vermilion ageing to pink, with a yellow flare on the upper lobe, 2 in. wide; bud and tube dark red (Ghent, before 1875). Tall growing.

‘Persil’. – White with a buttercup-yellow flare, 214 in. wide; trusses compact, with up to twenty flowers. Raised in the Knap Hill Nursery and distributed by Messrs Slocock. Although classed as a Knap Hill, it is near to the Ghents.

‘Phoebe’ (‘Phébé’). – Double, sulphur-yellow with a darker tube (Rustica fl.-pl.; C. Vuylsteke, 1888).

‘Queen Emma’ (‘Koningin Emma’). – Deep apricot-orange (Mollis; K. Wezelenburg and Son). A fine azalea that has never received an award in Britain, though highly rated in Holland. It is named after the grandmother of Queen Juliana of the Netherlands.

‘Redshank’. – Tangerine-orange, flushed with red; trusses with fifteen to twenty flowers, sometimes more (Knap Hill, 1947). A.M.T. May 26, 1953.

‘Sang de Gentbrugge’. – Rich tangerine-scarlet with a deep orange flare; tube yellow and pink (Ghent; L. van Houtte, 1973).

‘Silver Slipper’. – Creamy white with a yellow flare; bud, opening flower and its tube tinged with pink; fragrant (Knap Hill-Exbury, distributed by Waterer, Bagshot, 1948). A.M.T. June 7, 1962; F.C.C.T. 1963.

‘Spek’s Brilliant’. – Bright orange-scarlet with a deeper flare (Mollis; Jan Spek). The true variety is a clone, but seedlings are sometimes sold under the name.

‘Spek’s Orange’. – Bright orange with a greenish flare (Mollis; Jan Spek). F.C.C.T. May 26, 1953. As suggested by the date of the award, this clone is late-flowering for a Mollis azalea.

‘Strawberry Ice’. – Light flesh-pink, veined and flushed with deeper pink; flare yellow; truss with twenty or more flowers (Knap Hill-Exbury, distributed by Waterer, Bagshot). A.M.T. May 31, 1962. Recommended for an Award of Garden Merit.

‘Sunbeam’. (Altaclarense ‘Sunbeam’). – Chinese yellow flushed apricot, with a tangerine blotch (M. Koster and Sons, 1895). A.M.T. May 16, 1962. A hybrid of the yellow ‘Altaclarense’, usually classed as a Mollis.

‘Sun Chariot’. – Golden yellow with a flare of deeper yellow (Knap Hill-Exbury, distributed by Waterer, Bagshot). F.C.C.T. May 31, 1967. One of the finest yellows in the Knap Hill group, flowering in late May or early June.

‘Superba’. – Buff-pink in the bud, opening white flushed with pink, becoming pure white, margins frilled; flare yellow, large, occupying most of the central lobe (Occidentale Hybrid; M. Koster and Sons, 1901).

‘Sylphides’. – Pale pink with a flare of buttercup-yellow (Knap Hill). A.M.T. 1957.

‘Toucan’. – Corolla widely expanded, cream, fading to white, pink-tinged at the margins, flare large, yellow, fragrant (Knap Hill, 1941).

‘Unique’. – Orange-yellow in the bud, opening deep buff-yellow flushed with orange, upper lobe deep yellow. The very large trusses, up to fifty flowers, are composed of a terminal cluster supplemented by axillary ones (Ghent; in cultivation 1864). A.M.T. May 22, 1952.

‘Viscosepalum’. – Flowers very fragrant, twelve to fourteen in the truss; pedicels densely glandular. Buds buff at the tips with a green tube, opening ivory white with a small yellow flare, 134 in. wide, tube sticky with stalked glands. A hybrid between R. molle (Azalea sinensis) and R. viscosum, raised at the Knap Hill Nursery before 1842. The original plant is 9 ft high and 21 ft in spread. ‘Viscosepalum’ is much nearer to R. viscosum than is ‘Daviesii’, which has the same parentage but is more richly coloured and not so glandular.

‘Whitethroat’. – Pure white, double, 112 in. wide, in trusses of about eight (Knap Hill, 1941). A.M.T. May 19, 1962.

‘Willem Hardijzer’. – Porcelain Rose flushed with scarlet; flare orange (Mollis; W. Hardijzer and Co.). A.M.T. May 28, 1969.

‘Wryneck’. – Sulphur-yellow, flushed pink at the margins; flare yellow (Knap Hill).

Species articles

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