An evergreen shrub or tree said to attain almost 70 ft in the wild; young stems stout, glandular-downy when young. Leaves leathery, elliptic or elliptic-oblong, 2 to 5 in. long, 11⁄4 to 2 in. wide, obtuse at the apex, rounded or truncate to slightly cordate at the base, dark green and bullate above, clad beneath with a yellowish or rust-coloured, woolly indumentum, which is rather sticky to the touch owing to the presence of stalked glands amongst the hairs, margins strongly revolute; stalk stout, up to 3⁄4 in. long. Inflorescence as in R. arboreum; pedicels 3⁄8 to 1⁄2 in. long, glandular. Calyx small, irregularly five-lobed, densely glandular on the margin. Corolla rich scarlet, about 13⁄4 in. long. The flowering time is April-May, i.e., later than in R. arboreum. Bot. Mag., t. 7696. (s. and ss. Arboreum)
Native of Ceylon at 6,000 to 8,000 ft; introduced in the 1830s. Its original habitat was in the zone of temperate forest, of which vestiges still remain, and on the mountain summits, where it formed dwarf forest. At the present time it also occurs as isolated specimens in the patana grasslands, which are at least in part the result of the burning of the primaeval forest. One such specimen, growing on the golf-course at Nuwara Eliya, was 35 ft in height and spread and 93⁄4 ft in girth below the lowest branch, when measured in 1926 (C. Ingram, Gard. Chron., Vol. 80, p. 289 and fig. 134).
In the last century R. zeylanicum was commonly grown under the name R. rollissonii, and this would be the correct name for the species were it not that there is some doubt concerning the identity of the rhododendron described and figured under that name in 1843 (Bot. Reg., Vol. 29, t. 25). At the end of the last century it was grown at Kew under the name R. kingianum, in the belief that it had been raised from seeds collected by Sir George Watt in Manipur, and that it was the rhododendron for which he had proposed that name. But Dr Cowan later pointed out that the plant in question is obviously R. zeylanicum and that it does not in the least resemble the Manipur rhododendron, of which Sir George Watt's drawing and detailed manuscript description have been preserved (Notes Roy. Bot. Gard. Edin., Vol. 19 (1936), p. 161). But see further below.
Although closely related to R. arboreum, the Ceylon rhododendron is well distinguished from it by its relatively broader, bullate leaves, and by the presence of glands on their undersurface. It is uncommon in cultivation, but grows quite well, though slowly, in the milder parts and even seeds itself. The most notable specimens are at Stonefield and Arduaine in western Scotland. The latter is about 20 ft high, on eleven stems, and was raised from seeds brought from Ceylon in 1898 (R.C.Y.B. 1964, pp. 10-11; 1966, p. 35).
R. zeylanicum and R. nilagiricum are discussed by Dr J. M. Cowan in Notes Roy. Bot. Gard., Vol. 19 (1936), pp. 157-66.
R. nilagiricum Zenker R. arboreum var. nilagiricum (Zenker) C. B. CI.; R. arboreum of many authors, in part, not Sm. – Closely related to R. zeylanicum, differing in its narrower leaves without glands on the undersurface, and in its tomentose, not glandular, pedicels and calyx, the latter very small. Flowers scarlet, crimson, or pink. Native of S.W. India; described from the Nilgiri Hills and also found in the Anaimalai and Palni Hills, farther south. Whether R. nilagiricum and R. zeylanicum should be regarded as distinct species is debatable. If they are to be united, as they were by Dr Stapf (Bot. Mag., t. 9323), then the name for the combined species would be R. nilagiricum, which has long priority. But Cowan, in the article alluded to above, considered that they should be kept separate, remarking, however, that they are more closely allied to each other than either is to R. arboreum.
The rhododendron figured in Bot. Mag., t. 4381, as R. nilagiricum is not that species but R. arboreum.
R. kingianum Watt ex W. Watson R. arboreum var. kingianum Hook. f. – The name R. kingianum was proposed by Sir George Watt for a rhododendron found by him on Ching Sow, Manipur, in 1882, the original specimen of which is preserved in the Kew Herbarium (Watt 6535). He also sent seeds to Kew, and a plant raised from these was described by Sir Joseph Hooker in 1900 under the name R. arboreum var. kingianum (Bot. Mag., t. 7696). Cowan, in the paper referred to above, takes the view that R. kingianum, i.e., the plant raised at Kew, is R. zeylanicum. If this judgement is correct, two possibilities have to be considered: that Hooker was in error in supposing that the plant he described was raised from the seeds collected by Watt; or that R. zeylanicum occurs in Manipur. The latter possibility is far from unlikely. Numerous species of the eastern Himalaya and neighbouring mountains occur on the hills of peninsular India and Ceylon, or are represented there by closely related forms. Watt's 6535 is certainly near to R. zeylanicum in the shape and indumentum of its leaves (but perhaps even nearer to R. nilagiricum), and similar specimens have been collected in the Khasi Hills of Assam. The identity and status of R. kingianum is therefore best left in abeyance until the whole R. arboreum complex has been studied as a whole.
From the Supplement (Vol. V)
This becomes a subspecies of R. arboreum.
Since Volume III of this edition was published in 1976, numerous hybrids have come into commerce, some raised since that date, others, including a number from the USA, not then available in commercial quantities, if at all. In the following brief survey of these, F.C.C.T., A.M.T. and H.C.T. mean respectively First Class Certificate, Award of Merit and Highly Commended after trial in the R.H.S. Garden at Wisley in Surrey. Awards granted by the American Rhododendron Society are: S.P. A. (Superior Plant Award), A.E. (Award of Excellence), C.A. (Conditional Award) and P.A. (Preliminary Award). For further information on these, see the Quarterly Bulletin of the Society, Vol. 31 (Spring 1977), p. 105.
Elepidote Hybrids (other than those from R. yakushimanum)
American Hybrids. – 'Anna Rose Whitney', available from several nurserymen, has the parentage R. griersonianum × 'Countess of Derby'; the flowers are 31⁄2 to 4 in. across, carmine rose, opening in late May or early June. 'Buttermint', of low, compact growth and good foliage, is a hybrid of 'Unique', crossed with (Fabia × R. apodectum). 'Cadis' (A.E. 1959) is R. fortunei subsp. discolor crossed with 'Caroline', a hybrid of R. decorum with probably R. brachycarpum as the other parent. It is vigorous, of good habit, with frilled, light pink flowers about 33⁄4 in. wide, in June. 'C.I.S.' (A.M. 1973; A.M.T. 1975) is a hybrid from Fabia, the influence of which shows in the petaloid calyx and in the flowers, which when fully open are cream-coloured with apricot shading. The other parent was 'Loder's White'.
'Halfdan Lem' (named after its raiser) is said to be an improvement on 'The Hon. Jean Marie Montagu', which was one of the parents. 'Hotei' (A.M. 1974) is the result of a cross between 'Goldsworth Orange' and a seedling of R. souliei × R. wardii received (as seed) from Fred Rose, head gardener to Lord Swaythling at Townhill Park. The flowers are deep yellow, in May, freely borne on a compact plant.
One of the most notable introductions from the USA is 'Trude Webster' (S.P.A. 1971), the result of selfing 'Countess of Derby' ('Pink Pearl' × 'Cynthia'), with very large, pink flowers.
Other Hybrids. – Most of the elepidote hybrids to receive awards recently in the Wisley trials are hybrids of R. yakushimanum. An exception is 'Grenadine', (F.C.C.T 1982), an Exbury hybrid between R. griersonianum and 'Pauline' (of unknown parentage). The flowers, opening in May, are a good pink (near Delft Rose) deepening in the throat, with some speckling. Another award plant (A.M.T. 1983) is one of the Hobbie hybrids from a prostrate form of R. forrestii, 'Red Carpet'.
The most notable yellow-flowered hybrid raised in recent years is 'Kathleen Fortescue' (A.M.T. 1981), a cross between a selection of the Hawk grex and a hardy form of R. griffithianum, for which Lionel Fortescue was awarded the Cory cup shortly before he died in 1981. It flowers in late April or early May. 'Beatrice Keir', a fine hybrid between R. lacteum and 'Darmaris Logan', was raised at Windsor (A.M. 1974). The Exbury hybrid 'Prelude', the last to be raised in Lionel de Rothschild's lifetime, is in commerce and highly rated at Exbury. It is from R. fortunei × R. wardii and the American hybrid 'Golden Star' is also of this parentage. A promising German-raised hybrid is 'Rothenburg', with large acid-yellow flowers and bold foliage. It derives from 'Diane' and the other parent is stated to be R. williamsianum, which seems scarcely credible. Finally, it should be added that two other clones of Francis Hanger's Moonshine grex (page 875) are in commerce: 'Moonshine Bright' and 'Moonshine Crescent'.
'President Roosevelt' is a rhododendron that should not be bought sight unseen. The leaves have a bold central variegation of yellow and lighter shades of green; the flowers, opening in May, are purplish pink, paler at the centre, and would not be tolerated in a plant with normal foliage.
Hybrids of R. yakushimanum
The use of R. yakushimanum in breeding was mentioned on pages 826-7, and a few were included in the descriptive list. Only ten years later, the group has grown considerably (one nurseryman lists over thirty sorts) and many have received awards after trial at Wisley. It is impossible to do justice to these rhododendrons here, but most of those that have received awards are enumerated below. Those with pink flowers are mostly the result of crossing with red- or pink-flowered Hardy Hybrids. Red has come from R. griersonianum and R. facetum (eriogynum); yellowish and sunset shades from R. dichroanthum via Fabia clones; lavender (in two Hydon crosses) from 'Purple Splendour'; white probably in the main from R. yakushimanum itself The Waterer hybrids are the product of a breeding programme initiated by Messrs. Waterer, Son and Crisp; the Hydon hybrids were raised by Arthur George at the Hydon Nursery near Godalming.
Pink. – 'Diana Pearson' (Hydon; A.M. 1978); 'Doc' (Waterer; H.C.T. 1978); 'Hydon Dawn' (Hydon; A.M. 1978); 'Marion Street' (John Street; A.M. 1978); 'Star Shine' (Waterer; A.M.T. 1977); 'Surrey Heath' (Waterer; A.M.T. 1982).
Red. – 'Dopey' (Waterer; A.M.T. 1977); 'Hydon Hunter' (F.C.C. 1977); 'Venetian Chimes' (Waterer; A.M.T. 1979).
Lavender. – 'Caroline Albrook' (Hydon; A.M.T. 1977); 'Ernest Inman' (Hydon; A.M.T. 1979).
Yellowish and Mixed. – 'Golden Torch' (A.M.T. 1984);
'Grumpy'(A.M.T. 1979); 'Percy Wiseman' (A.M.T. 1982). All these are Waterer hybrids.
White. – 'Hoppy' (Waterer; A.M.T. 1977); 'Hydon Ball' (Hydon; A.M.T. 1977); 'Lady Romsey' (Edmund de Rothschild, Exbury; A.M. 1982); 'Morning Magic' (Hydon; A.M.T. 1982).
'Seven Stars' (F.C.C.T. 1974), mentioned on page 893, is one of the finest R. yakushimanum hybrids, but is likely to attain a fairly large size in time.
Some consider that crosses between R. yakushimanum and other species are more attractive than those which have a hybrid as the other parent. Mention was made on page 897 of 'Streatley'. Others raised at Windsor are 'Bradfield' and 'Swallowfield' (both with R. souliei) and 'Wishmoor' (with R. litiense, now included in R. wardii).
These are lumped with the elepidote hybrids in the main work, but there is much to be said for treating them separately, as they are as distinct from them horticulturally as they are botanically.
Three of Peter Cox's hybrids are mentioned in the descriptive list – 'Curlew', 'Phalarope' and 'Ptarmigan'. More recent introductions in his Bird series are the yellow-flowered 'Chiff Chaff' (R. hanceanum 'Nanum' × R. fletcherianum; A.M. 1976); 'Goosander' (R. lutescens × R. ludlowii; A.M.T. 1981); 'Teal' (R. brachyanthum × R. fletcherianum; A.M. 1977); and 'Woodchat' (R. brachyanthum × R. ludlowii; H.C.T. 1982). Also 'Euan Cox' (R. hanceanum 'Nanum' × R. ludlowii; A.M.T. 1981), crossed by Peter Cox's father, the well-known plantsman E. H. M. Cox (d. 1977). These are all dwarf, the tallest being 'Teal' (to about 3 ft), and flower in May.
Others in Peter Cox's Bird series are 'Razorbill', a seedling of R. spinuliferum, of dwarf habit with bright pink flowers in dense clusters opening in late April or early May (F.C.C.T. 1983); and 'Eider' (A.M.T. 1981), the result of a cross between a white-flowered R. minus (in the form previously known as R. carolinianum) and R. leucaspis. It grows to about 2 ft high and produces its white flowers in April.
'Blue Chip' (A.M. 1978) is an April-flowering rhododendron raised by Arthur George at the Hydon Nursery from Blue Diamond crossed with R. russatum. The German 'Azurwolke' is the same parentage.
American Hybrids. – The best known and most widely available of these is 'Dora Amateis' (F.C.C.T. 1981), which makes a compact plant bearing abundant white, lightly speckled flowers about 2 in. wide in April. It was raised by the sculptor Edmond Amateis from R. minus (carolinianum) crossed with R. ciliatum. Another hybrid of R. minus (seed-parent) is 'Ramapo', which has R. fastigiatum as the pollen-parent and takes after it in its glaucous foliage; the flowers are light purple in April or May.
The P.J.M. grex (R. minus × R. dauricum) is widely grown in the colder parts of North America for its hardiness and early flowers. The initials stand for P. J. Mezitt, at whose Weston Nursery in Massachusetts the cross was made. The clonal name 'P. J. Mezitt' belongs to the form exhibited by the Crown Estate Commissioners on March 28 1972, when it received an Award of Merit. In this the flowers are a light rosy purple. The group varies somewhat in colour and is an improvement on R. dauricum.
Two American hybrids deriving from R. mucronulatum are 'Airy Fairy' (A.M.T. 1984), from a cross with R. lutescens, with light pink, speckled flowers in March; and 'Anna Baldsiefen' (H.C.T. 1979), semi-dwarf with pink flowers in April, which came from the selfing of 'Pioneer', a cross between R. mucronulatum and R. racemosum.
'Maricee' (A.E. 1959; A.M.T. 1984) is a hybrid seedling of R. sargentianum and for garden purposes an improvement on it, as it bears its white flowers more freely. Finally, mention should be made of 'Cutie' (A.E. 1962), a free-flowering seedling of R. calostrotum with purplish pink flowers; the other parent is thought to have been R. racemosum.
It should be noted that in the introductory paragraph on page 904 R. japonicum means the azalea species incorrectly so named.
Two interesting new American azaleodendrons are now available in Britain, both R. maximum × R. occidentale. – 'Jock Brydon' and 'Martha Isaacson'. A natural hybrid between R. occidentale and R. macrophyllum was found in Oregon some decades ago and propagated as 'Oregon Queen'.
An addition to the Hardijzer group (page 905, and 'Ria Hardijzer', page 908) is 'Lilian Harvey' (R. racemosum × 'Hatsugiri'; A.M.T. 1983).
AZALEA HYBRIDS – DECIDUOUS
It was remarked on page 910 of this group: 'At the present time they are quite overshadowed by the large-flowered modern hybrids. This is a pity . . .' Others agree and it is welcome news that a comprehensive collection of Ghent azaleas is being formed in the National Trust garden at Sheffield Park in Sussex, and also in the Valley Gardens at Windsor and in the Royal Botanic Garden, Edinburgh. A protective hand might be extended to other azaleas which are now unfashionable because their flowers are too small or too modestly coloured. For example, the lovely 'Daviesii' seems to have become scarce. It was, incidentally, omitted from the description (on page 916) that the flowers are deliciously fragrant.
No mention was made in the introductory note of the Cote grex of deciduous azaleas, raised by Mr and Mrs J. B. Stevenson at Tower Court, Ascot, in the 1930s from R. atlanticum crossed with other azaleas. A number of clones were put into commerce about twenty years later, of which 'Tower Dainty' received an Award of Merit in 1983. The scented flowers in this group are in shades of pink and salmon.
AZALEA HYBRIDS – EVERGREEN
An account was given on pages 925-34 of the evergreen azalea hybrids most widely available in commerce around 1975. An additional list as long as this could now be included, but it is questionable whether the amount of variation in this group is sufficient to accommodate more than a fairly limited number of really distinct cultivars. Many of the pink-flowered Malvatica × kaempferi hybrids effectively duplicate each other to the extent of being almost indistinguishable, and the 450 or so Glenn Dale hybrids tend to fall into clusters, each with the same habit, flowering season, corolla form and colour.
The following have received awards recently after trial at Wisley; all flower in the second half of May ('Mahler' in late May or early June): 'Blue Danube' (F.C.C.T 1975), with smallish purple flowers on a low, spreading bush, raised in Belgium; the Dutch 'Lily Marleen' (A.M.T. 1982), with small hose-in-hose flowers in a deep shade of rosy pink; 'Mahler' (F.C.C.T. 1976), of spreading habit with fairly large Petunia Purple flowers; 'Mimi' (A.M.T. 1975), with large silvery rose flowers; and 'Velvet Gown' (A.M.T. 1982), bred at the Waterer Nurseries, Bagshot, with Mallow Purple flowers about 13⁄4 in. wide, very freely borne.
Mention was made on page 927 of the Gumpo azaleas deriving from R. eriocarpum. From these Mr Wada raised a group of hybrids with R. kaempferi as the other parent, of which the best known is the late-flowering 'Bungonishiki', with more or less double terracotta red flowers and of compact habit. One of this so called Wadai group, crossed at Windsor with Mucronatum, has produced 'Snow Hill' (A.M.T. 1978), which makes a low, spreading bush bearing white flowers about 23⁄4 in. wide in early June.
An interesting Kurume-type azalea now in commerce is 'Ward's Ruby', which was distributed by Domoto Brothers of California and almost certainly came from Japan, from which they imported many Kurumes. Indeed, as Frederic Lee points out in his The Azalea Book, many of the Wilson Fifty actually reached the trade in the USA through this firm directly from Japan. 'Ward's Ruby' has crimson-scarlet flowers and received a Preliminary Commendation in 1977 when shown at Vincent Square by the late Collingwood Ingram, who received his plant from Domoto Brothers. Another azalea of the Kurume type is the Dutch 'Kermesina', with carmine flowers opening in the latter half of May. Its origin is apparently unrecorded.
The Eira group of hybrids were raised in the late 1930s by J. B. and Mrs Stevenson at Tower Court from the Kurume 'Kirishima' crossed with 'Malvaticum' and, named after Gilbert and Sullivan characters, were later distributed by the Hydon Nursery. 'Pooh Bah' (H.C.T. 1982) has Mallow Purple flowers about 13⁄4 in. wide. From one of the Eira group crossed with R. kaempferi, Arthur George raised 'Mary Meredith' (A.M.T. 1979), with deep pink flowers about 11⁄2 in. wide. Both these flower in late May.
R. kiusianum, an attractive species in its own right, has also become the parent of hybrids. The Diamant group were bred in Germany from this species and various Kurume azaleas. They come in a wide range of colours and are low-growing. Peter Cox's 'Panda' (H.C.T. 1984) is the result of a cross between R. kiusianum 'Chidori' and 'Everest', and makes a dense bush with white flowers in late May or early June.
Peter Cox has also used the very late-flowering R. nakaharae to produce three low-growing hybrids: 'Lemur', 'Squirrel' and 'Wombat'.
American Hybrids. – The Glenn Dale azaleas are mentioned on page 924 and a few were included in the descriptive list. More are now available than ten years ago, of particular value being those that flower in the latter part of May or even in early June. Awarded with a Highly Commended in the Wisley trials are the white-flowered 'Niagara', 'Everest' and 'Eucharis', and a sister seedling of the last-named, also excellent, is 'Polar Sea', flowering around mid-May. 'Niagara' is one of the forty or so azaleas that Mr Morrison raised from the complex cross mentioned on page 932, under 'Silver Moon'. The other three derive from the Japanese Satsuki azalea 'Shinnyo-no-tsuki'. This is also a parent of 'Martha Hitchcock', mentioned on page 929, where it was incorrectly stated that 'Shinnyo-no-tsuki' derives from an Indian Azalea named 'Elizabeth'. Correct is 'Albert-Elisabeth', which was once much used for conservatory and house decoration and is almost certainly still in cultivation; the flowers are semi-double, white with an edge of deep pink.
The Glenn Dale cross between R. indicum and 'Hazel Dawson' (R. kaempferi × Mucronatum) produced three late-flowering azaleas, all with pink flowers and all available in commerce: 'Elizabeth', 'Gaiety' and 'Megan'. Another of the offspring of 'Shinnyo-no-tsuki' is 'Louise Dowdle' (A.M.T. 1973), with pink flowers in late May or early June.
The above all have flowers around 3 in. wide. With smaller flowers and mostly mid-season are 'Bravo' (pink), 'Chanticleer' (purple), both with the same parentage as 'Niagara' and 'Silver Moon' (see above); 'Dayspring' (white margined with pink) and 'Galathea' (orange).
Of the Gable hybrids (page 925), 'Rosebud' and Stewartstonian' are well known both here and in the USA, and are mentioned in the descriptive list. Others are 'Lorna', similar to 'Rosebud' but paler; 'Purple Splendour' (R. yedoense var. poukhanense × 'Hexe'), with hose-in-hose reddish violet flowers ('Herbert' is similar and of the same parentage); and 'Louise Gable' (H.C.T. 1973), with deep violet-red flowers.
'Hino Crimson' (A.M.T. 1974), a Kurume-type azalea, is hardier than 'Hinodegiri', which is the pollen-parent, the seed-parent being 'Amoenum'. It was raised, or at least distributed, by J. Vermeulen of Bridgeton, New York, and has carmine-red flowers in early May. It should be added that the azalea appearing frequently in American lists under the name 'Coral Bells' is the Kurume 'Kirin'.
Of recent introduction to Britain are the hardy Robin Hill azaleas, bred by Robert Gartrell in New Jersey from Japanese Satsukis, R. kaempferi and various Glenn Dale and Gable hybrids. The flowers are mostly 3 in. wide or over and borne late in the season. Notable among these is 'Nancy of Robin Hill', named by the raiser after his wife, with rosy pink hose-in-hose flowers.