The name ‘Azaleodendron’ was coined by Rodigas in 1892 for hybrids between the Japanese azalea R. japonicum (the Azalea mollis of gardens) and various Hardy Hybrid rhododendrons, raised at Ghent a few years previously (see further below). The following year it was taken up by Dr Masters as a sectional name under Rhododendron. In Rehder’s classification of the genus, all the azaleas are grouped in a single subgenus (Anthodendron), and all the remaining species (except the azaleastrums), in another subgenus (Eurhododendron). The azaleodendrons, being hybrids between these two major groups, were given the rank of a separate subgenus – subgen. Azaleodendron (Rodigas) Rehd. In modern classifications, Rehder’s two main groups (Eurhododendron and Anthodendron) are split into two or more subgenera but as it happens, all the known azaleodendrons, with the exception of the Hardijzer group, are of similar parentage to the type of the subgenus Azaleodendron, being crosses between (in modern nomenclature) the subgenera Azalea and Hymenanthes, and therefore constitute a single subgenus, for which the name Azaleodendron continues to be valid. Attention is called to this fact since it is often assumed that the term ‘azaleodendron’ is merely a horticultural coinage of no botanical standing, when in fact it is only invalid when used as a generic name.
In the last century numerous azaleodendrons were raised, of which few survive, no doubt because the majority lacked vigour. Those still grown mostly have ugly foliage and are tolerated only because of their striking flowers. Considering how many azaleodendrons were raised in the last century, Lionel de Rothschild’s failure in breeding them is interesting. For two years running he crossed any hybrid rhododendron he had in flower with four different types of azalea, making the crosses both ways – fifty or sixty crosses each year all told. From these he got one pod of seed and raised three seedlings, which had not flowered at the time he wrote (Y.B. Rhod. Ass. J934, pp. 113-14). There is no further record of these, so presumably they were worthless.
Most of the azaleodendrons in cultivation are described below. The Belgian hybrids to which the name Azaleodendron was first applied seem mostly to have dropped out of cultivation, except for ‘Dr Masters’, not seen, described as having rosy flowers tinted with lilac, heavily spotted on the upper lobe. They were raised by van der Meulen from R. japonicum crossed with hardy hybrids, including ‘Prince Camille de Rohan’ and ‘John Waterer’.
Hardijzer Group
Although it would be reasonable to term these hybrids ‘azaleodendrons’ in the horticultural sense, they are of quite different parentage to those discussed above, one parent being the lepidote R. racemosum, the other a Kurume azalea. In Sleumer’s classification the former is placed in the subgenus Pseudorhodorastrum; the latter belongs to the subgenus Tsutsia. See further under ‘Ria Hardijzer’.
DESCRIPTIONS
Azaleoides. – The name R. azaleoides starts in a French work – Dumont de Courset’s Botaniste Cultivateur, Vol. III (1811). The plant described had come from England, and there is little doubt that it was the hybrid raised at Thompson’s nursery at Mile End, near London, from R. ponticum pollinated by some azalea – possibly R. periclymenoides (nudiflorum). It is figured in Andrews’ Botanical Repository, t. 379 (1804), under the name R. ponticum var. deciduum, though R. azaleoides was apparently the name used for the hybrid by the nursery. At any rate, Sims stated in 1822 that Thompson had four varieties under the name R. azaleoides, one of which had scented flowers. This name has been a source of confusion, since it was used more or less in the same sense as the modern term ‘azaleodendron’ and applied later to other hybrids of this character. The azaleodendron described in previous editions of this work under the name R. azaleoides is most probably a hybrid between R. viscosum and R. maximum and, as Rehder pointed out, does not resemble the Thompson plant figured by Andrews. Whether the original R. azaleoides is still in cultivation it is impossible to say.
‘Broughtonii Aureum’ (‘Norbitonense Broughtonianum’). – Truss 4 in. wide, with eight to sixteen flowers on downy stalks 1 to 11⁄2 in. long. Calyx-lobes pale green, of unequal length, oblong. Corolla 21⁄2 in. wide, of a beautiful soft, primrose yellow, with reddish-brown spots in the upper part. Stamens ten. Leaves narrowly obovate or oblong, 2 to 6 in. long, 3⁄4 to 13⁄4 in. wide, dark dull green above, pale green and prominently net-veined beneath, covered with pale down on both sides. An almost evergreen shrub eventually 6 ft high. Late May or early June.
Similar to this is ‘Smithii Aureum’ (‘Norbitonense Aureum’), which differs in having the leaves very glaucous beneath; its flowers too are of a paler colour and not so flat and open; the flower-stalk is longer and more slender, and the calyx-lobes somewhat narrower. ‘Broughtonii Aureum’ is the better shrub – more beautiful and growing better.
These two azaleodendrons seem to be the only two that have survived of the ‘Norbiton Hybrids’ (R. norbitonense André), also known as ‘Smith’s Yellow Rhododendrons’. They were raised by William Smith, who had been gardener to the Earl of Liverpool at Coombe Wood House, near Kingston-on-Thames, and around 1830 set up his own nursery a mile or so away on Norbiton Common. He was one of the most adventurous hybridisers of his day, his best known production, apart from his yellow azaleodendrons, being the cross between R. arboreum and R. ponticum named after him, various Indian azaleas, and one of the first ‘lepidote × elepidote’ crosses. He died before 1846 and was succeeded by J. B. Smith.
The first of Smith’s ‘yellow rhododendrons’ were raised around 1830 and three were shown in the Ghent Exhibition in 1839 ‘au grand étonnement des amateurs’. A second and larger set was raised in the late 1830s. At least nine were raised in addition to the two described here and all these are listed and described by the French horticulturalist André in 1864. ‘Smithii Aureum’ is the best documented of the set. It was figured in 1842 in Paxton’s Magazine of Botany and is the result of a cross between R. molle (Azalea sinensis) and Smith’s own white-flowered hybrid between R. ponticum and R. maximum. The original plant was bought by Lucombe and Pince of Exeter, who distributed the clone under the name R. aureum (Gard. Chron. (1843), p. 425). The parentage of ‘Broughtonii Aureum’ is not recorded, but in view of its similarity to ‘Smithii Aureum’ it is likely to have been of the same parentage. Watson’s assertion, in Rhododendrons and Azaleas (1911), that ‘Broughtonii Aureum’ was raised at Broughton in Peebles-shire was the result of an uninspired guess. The well-known dendrologist F. R. S. Balfour of Dawyck, in the same county, took the trouble to make enquiries at Broughton when the first edition of this work was being prepared, and found no memory or record of there ever having been a nursery there. The name ‘R. Broughtonianum’ appears in André’s list of the Smith azaleodendrons, and there is little doubt that the name commemorates Sir J. D. Broughton, who had a garden at Kingston not far from Smith’s nursery and held the entire stock of many of his azalea hybrids, which he bought as seedlings after they had first flowered (Gard. Chron. (1842), p. 743). Two azaleas were also named after him, one by Smith, another by Jackson, also of Kingston.
According to André, many of the Smith azaleodendrons were introduced to France by Paillet, and became the vogue in the years 1845-50, when they were ‘le sujet de toutes les conversations horticoles et de tous les soins des cultivateurs’. But the fashion passed when it was found that the plants were of poor constitution and sparse in their foliage. Andre’s account is to be found in his book Plantes de Terre de Bruyères, published in 1864. At that time he was already Chief Gardener of the City of Paris, at the age of twenty-four.
Fragrans. – Flowers very fragrant, in clusters of twelve to twenty; pedicels 3⁄4 to 1 in. long, glandular. Calyx-lobes linear-triangular, 1⁄8 to 1⁄4 in. long, downy and glandular. Corolla funnel-shaped, about 11⁄4 in. long and wide, white at the centre, deeply and unequally finged at the edge with purplish lilac, downy outside and in the throat. Stamens ten, very hairy at the base, Leaves persistent except in hard winters, oblanceolate, 2 to 4 in. long, 1⁄2 to 11⁄2 in. wide, tapering gradually to the base, more abruptly to the short point, dark glossy green above, glaucous beneath, quite glabrous when mature. A slow-growing bush, eventually up to 6 ft high and more in width, flowering in June or early July.
A hybrid of the azalea R. viscosum, crossed with R. maximum, R. ponticum, or R. catawbiense, or with a hybrid involving two of these species. Many crosses of this type were made in the first half of the 19th century, and the resulting hybrids all had flowers in some shade of lilac or purple with a white centre, and many were fragrant. R. periclymenoides (nudiflorum) was also used, with similar results. The plant here described, which may be one of several very similar clones, has also been known as R. odoratum and, wrongly according to Rehder, as R. azaleoides. It agrees well with a hybrid grown in gardens under the name R. fragrans as early as 1835, which was figured in Bot. Mag., t. 3454, as ‘R. maximum hybridum’. Sir William Hooker renamed it thus in the belief that it was the same as the hybrid between ‘the common white glaucous-leaved azalea’ and R. maximum, which was raised by the Rev. William Herbert at Spofforth, and was figured in Bot. Reg., t. 195 (1817), under the name R. hybridum. The present plant and the two depicted in these works certainly agree quite well. Later, in 1843, the name R. fragrans was used by Paxton for an azaleodendron raised by the nurseryman Chandler of Vauxhall some twenty-five or thirty years previously (Paxton’s Mag. Bot., Vol. X, p. 147, t.). The seed-parent was said to have been R. catawbiense, though it may in fact have been R. ponticum. However, this plant was said to be very dwarf and compact, with the leaves ‘a little wrinkled and destitute of much glossiness’. This does not sound like the plant here described, which is more likely to be the same as R. hybridum. That at any rate was Rehder’s opinion (Monogr. Azaleas (1921), p. 190), but in view of the uncertainties as to the history and parentage of the R. fragrans of gardens it seems better to adhere to the familiar name.
Also in cultivation is ‘Govenianum’, which may represent a single clone. It resembles the plant described in most respects, including the glaucous undersurface of the leaf, but the flowers are of a darker shade, and the calyx-lobes narrower and more strap-shaped. The hybrid described by Sweet in 1828 under the name R. Gowenianum was raised by Gowen at Highclere from either R. viscosum or R periclymenoides pollinated by a hybrid of R. ponticum and R. catawbiense (Brit. Fl. Gard., t. 263 (1828)). But it is possible that the plant now cultivated is the result of some unrecorded cross made by Gowen, similar to that made by the Rev. William Herbert, who was the brother of the second Earl of Carnarvon, the owner of Highclere and patron of Gowen.
Gowen also made a cross at Highclere in 1825 between R. periclymenoides and R. catawbiense (pollen-parent), from which 97 plants were raised; the best was named ‘Carton’s Rhododendron’ by Lindley, after the head gardener there (Bot. Reg., t. 1449 (1831)). This was given botanical status by de Candolle as R. cartonianum (syn. R. cartoni Bean).
‘Galloper Light’. – Flowers about twelve in a rather loose truss, on glandular-downy pedicels. Corolla 2 in. wide, funnel-shaped, strawberry pink on a cream base, with a yellow flare in the upper part, the pink coloration fading as the flower ages. Leaves semi-deciduous, rugose, dark green. A hardy vigorous hybrid of unknown parentage, growing to 6 ft high. Late May or early June. It received an Award of Merit when shown by Lionel de Rothschild in 1927 but was raised at the Knap Hill Nursery, not at Exbury.
‘Gemmiferum’. – Flowers in a dense truss 3 in. across, on sticky, downy pedicels. Corolla funnel-shaped, 11⁄4 in. long and wide, of a more or less uniform purplish rose. Calyx-lobes 1⁄8 in. long, linear, hairy on the margins. Leaves 2 to 31⁄2 in. long, 1 to 11⁄2 in. wide, obovate to oval, downy beneath when young, becoming glabrous with age, dark glossy green above, pale green beneath, margins recurved. It makes an evergreen bush of rather loose habit up to 6 ft high, flowering in May or early June. Of unknown origin and parentage. Rehder suggests it might be a hybrid between the azalea R. prinophyllum (roseum) and R. catawbiense.
‘Glory of Littleworth’. – Truss compact, hemispherical, with fifteen to eighteen flowers; rachis 21⁄4 in. long; pedicels 1 to 11⁄2 in. long, glandular-downy. Corolla 2 in. wide with a slender tube, fragrant, cream fading to milky white, with a large blotch of coppery orange spots. Stamens six to eight. Leaves oblong-lanceolate with impressed laterals. Late May or early June. A lovely but rather demanding plant, not often seen in good condition. It received an Award of Merit on May 23, 1911, when shown by Miss Clara Mangles of Little-worth Cross near Farnham and was almost certainly raised there by her brother Henry Mangles (d. 1908), who, like his brother James Mangles (d. 1884), was a keen hybridiser.
‘Nellie’. – Flowers about twelve in a hemispherical truss, on glandular pedicels. Corolla funnel-shaped with a narrow tube, almost 21⁄2 in. wide, with a large yellow blotch, glandular on the outside, lobes wavy and somewhat recurved. Stamens ten. Leaves semi-deciduous, up to 4 in. long and 11⁄2 in. wide. June. Raised by Harry White at the Sunningdale Nursery. Probably R. occidentale is the azalea-parent.
‘Ria Hardijzer’. – Flowers crowded in a pseudo-terminal cluster, made up of several distinct axillary inflorescences, each with about three flowers, on white-hairy pedicels. Corolla funnel-shaped, 1 in. or slightly more wide, deep pink, slightly speckled in the throat. Stamens variable in number, more than five. Ovary clad with ascending white hairs. Leaves elliptic to slightly obovate, 3⁄4 to 1 in. long, scaly beneath, the upper ones persistent, the lower ones deciduous. Dwarf, compact habit. Two other hybrids in this group, with similarly coloured flowers are: ‘Hardijzer Beauty’, which is more robust than the preceding, with leaves up to 2 in. long, and with more flowers in the total cluster – up to sixty (A.M.T. May 12, 1970); and ‘Martine’, similar to ‘Hardijzer Beauty’ but of dwarfer habit with smaller leaves; the ovary is scaly.
These interesting hybrids were raised by P. W. Hardijzer in Holland and put into commerce by W. Hardijzer and Co. One parent is R. racemosum and the other a Kurume azalea, the influence of the first showing in the inflorescence and the presence of scales on one or more parts, and of the latter in the presence on the stems of appressed, strigose hairs of the type characteristic of the Obtusum subseries (subg. Tsutsia), and the reduced number of stamens. These hybrids are not azaleodendrons in the botanical sense. They represent a distinct hybrid subgenus, so far unnamed.
‘Torlonianum’. – Flowers about twelve in a dome-shaped truss. Corolla funnel-shaped, 13⁄4 in. or slightly more wide, rosy lilac with a conspicuous orange blotch, tube narrow, downy inside and out. Calyx-lobes linear, ciliate. Stamens nine. Leaves persistent, elliptic, glossy and reticulate above. Medium size. Late May. Of unknown parentage and origin, raised before 1845. Rehder suggests it is R. calendulaceum crossed with R. catawbiense.