Rhododendron Cultivars R

Racil (ciliatum × racemosum)

Flowers arranged as in R. racemosum, i.e., from upper axillary as well as terminal buds, one to three from each bud and forming a cluster of up to 20 flowers in all. Corolla pale pink, funnel-campanulate, about 1 in. wide. Calyx with long hairs at the edge, scaly. Leaves obovate, obtuse, coloured more or less as in R. ciliatum, 21⁄2 by 13⁄8 in. Erect, to about 5 ft. April. There appear to be several clones of this rather dull hybrid; the description is of one in commerce. The Award of Merit was given in 1957 to clone ‘Halbury’.

Rhododendron Racil (Ray Wood, Castle Howard, North Yorkshire, UK, April 2020). Image John Grimshaw.

'Rashomon'

Corolla 11⁄4 in. wide with a short tube, scarlet. Calyx well developed, with oblong, obtuse lobes. Dense habit, eventually 5 ft high (Kurume; Wilson No. 37).

Rhododendron 'Rashomon' at the Savill Garden, Windsor Great Park, UK. 26 May 2021. Image Tom Christian.

Rhododendron 'Rashomon' at the Savill Garden, Windsor Great Park, UK. 26 May 2021. Image Tom Christian.

Red Admiral (arboreum × thomsonii)

Harrisii (arboreum × thomsonii). – This cross was first made about 1880 in Lord Swansea’s garden at Singleton near Swansea by his head gardener Harris, who later set up his own nursery. The original plants were up to 25 ft high when Millais saw them in 1915.

The cross was later made at Caerhays with better results and the plants from this cross are usually treated as a separate grex under the name Red Admiral.

It was also made at Penjerrick, where it was named Tregedna. These hybrids are as early flowering as R. arboreum, and not common outside the milder parts. The flowers are fewer in the truss than in R. arboreum, with a more pronounced calyx, and vary in colour from crimson to blood-red. The leaves are usually (to the naked eye) glabrous beneath, relatively broader than in R. arboreum and usually obtuse at the apex.

Rhododendron Red Admiral at Exbury, Hampshire, UK. 21 March 2006. Image John Anderson.

An individual truss on Rhododendron Red Admiral at Exbury, Hampshire, UK. 21 March 2012. Image John Anderson.

Red Cap (eriogynum × sanguineum subsp. didymum)

Flowers six to eight in the truss; pedicels glandular and floccose. Corolla campanulate, 11⁄2 to 2 in. wide, dark red. Style red at the apex, with a dark stigma. Leaves narrowly oblong-obovate to almost elliptic, 31⁄4 by 11⁄4 in., medium green and fairly glossy above, coated beneath with a pale woolly tomentum. Of semi-dwarf, rather open habit. Late June or early July. This cross was made by J. B. Stevenson at Tower Court, also at Borde Hill, Exbury, and Townhill Park. The A.M. was given in 1945 to ‘Townhill Red Cap’, when shown by Lord Swaythling, but the description given above is from a plant at Borde Hill. There is probably little variation in this grex, which is inferior to the Arthur Osborn grex, from which it differs in the campanulate corolla.

'Redshank'

Tangerine-orange, flushed with red; trusses with fifteen to twenty flowers, sometimes more (Knap Hill, 1947). A.M.T. May 26, 1953.

Remo (lutescens × valentinianum)

Flowers from terminal and uppermost axillary buds, one or two from each bud. Corolla tubular-funnel-shaped, 1 3⁄4 in. wide, clear light yellow, with two lines of deeper speckles in the upper part. Calyx-lobes scaly and ciliate, lanceolate. Leaves elliptic, 2 1⁄4 in. long, acute to acuminate at the apex, edged with scattered hairs, sparsely scaly on both sides. Low growing. April. (Stevenson.) It is rather tender.

Rhododendron Remo at the Sir Harold Hillier Gardens, Hampshire, UK. 15 May 2021. Image John Anderson.

'Revlon'

The cross (cinnabarinum var. roylei × ‘Lady Chamberlain’) was made at Exbury, the result being ‘Revlon’, with flowers carmine on the outside, said to be very fine but still scarce in commerce. A.M. 1957. Flowers somewhat later than ‘Lady Chamberlain’.

'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.

'Robert Keir'

Flowers 14 in a full, rounded truss. Corolla funnel-campanulate with a spreading limb, mostly seven-lobed, 3 1⁄4 in. wide, at first creamy white overlaid with pink, at length ivory-white with a yellow flush in the throat. Leaves broad-elliptic, rounded and apiculate at the apex, about 8 in. long, half as wide. April. (lacteum × ‘Luscombei’.) This fine hybrid was raised at Tower Court, and is named after Robert Keir, who was for many years head gardener there, first to J. B. Stevenson and later to Mrs Stevenson. A. M. 1957.

Rhododendron 'Robert Keir' in the Valley Gardens, Windsor Great Park, UK. 1 May 2020. Image John Anderson.

Close up on a truss of Rhododendron 'Robert Keir' in the Valley Gardens, Windsor Great Park, UK. 1 May 2020. Image John Anderson.

'Roberte'

In ‘Roberte’ the flowers are delicate salmon-pink, fading to yellowish at the centre of each lobe (F.C.C. 1936).

See notes for Lady Bessborough (campylocarpum “var. elatum” × discolor)

Romany Chai (griersonianum × 'Moser's Maroon')

Similar to Romany Chal, but the colour of the flowers is not quite so good, and the corolla is funnel-shaped at the base. It is perhaps rather more hardy.

Romany Chal (eriogynum × 'Moser's Maroon')

Flowers about 12 in a lax truss; pedicels downy and sparsely stellate-hairy. Corolla campanulate, 2 3⁄8 in. wide, deep glowing red with markings on the upper lobes. Anthers black. Style red with a black stigma. Calyx crimson, with ovate, reflexed lobes. Leaves oblong-elliptic, 5 in. long, dull green, thinly brown-tomentose beneath. Vigorous, eventually making a tall pyramid. Late June. (Rothschild. F.C.C. 1937.) A splendidly coloured hybrid, at its best in light woodland. There is a fine group in the Valley Gardens, Windsor Great Park.

Rhododendron Romany Chal in the Valley Gardens, Windsor Great Park, UK. 6 June 2019. Image John Anderson.

Bold foliage on Rhododendron Romany Chal in the Valley Gardens, Windsor Great Park, UK. 5 June 2020. Image John Anderson.

'Rosebud'

Corolla 13⁄4 in. wide, Phlox Pink (62b), double, most of the stamens being converted into petals or staminodes. Calyx enlarged, up to 5/8 in. deep, green, or partly or wholly coloured like the corolla. Late May or early June. Spreading habit, ultimate height uncertain (Gable, USA). A charming azalea with truly double flowers, after the style of R. indicum ‘Balsaminiflorum’. A.M.T. 1972.

'Rosenkavalier'

A back-cross of Tally-Ho with R. eriogynum, raised in the R.H.S. Garden at Wisley, received an A.M. in 1959 under the name ‘Rosenkavalier’

'Roseum Elegans'

Flowers about twenty in a rounded truss. Corolla funnel-shaped, 25⁄8 in. wide, rosy lilac, with a small brown flare. Ovary purplish brown, almost glabrous. Early June. An old hybrid of R. ponticum, raised at Knap Hill and still in commerce.

'Rosy Bell'

Flowers about five per truss. Corolla campanulate, about 13⁄4 in. wide, appleblossom-pink, unmarked. Calyx lobed to the base, with spreading, ovate segments about 3⁄8 in. long. Leaves elliptic, acuminate, tapered at the base, up to 2 in. long and 3⁄4 to 1 in. wide. Dwarf, rather spreading habit. Late April or early May. (ciliatum × glaucophyllum; Isaac Davies, 1882. A.M. 1894, when exhibited by Kew.) A delightful hybrid, whose display is sometimes spoilt by frost.

The hybrid between R. ciliatum and R. glaucophyllum was also raised by Thomas Nuttall before 1859 and is figured in Bot. Mag., t. 5116, under the name R. wilsonii. which Nuttall chose to commemorate his friend W. Wilson the cryptogamist.

A back-cross of R. glaucophyllum onto Rosy Bell was raised by T. C. Thacker of Knowle, Warwickshire, and has been named ‘Arden Belle’. It resembles the former closely, differing in its greener more glossy foliage.

Royal Flush (cinnabarinum × maddenii)

This hybrid, raised by J. C. Williams at Caerhays shortly before 1917, is best known as a parent of Lady Chamberlain and Lady Rosebery. The seed-parent was R. cinnabarinum var. roylei and the pollen-parent an early-flowering form of R. maddenii grown at Heligan and known as ‘Heljackii’. The seedlings bore lapageria-like flowers in shades of orange-yellow or pink and are decidedly bud-tender. What is usually called the ‘orange form’ of Royal Flush is a lovely plant with fleshy, tubular-campanulate flowers buff-yellow inside with an orange throat, orange-pink outside. The cross had previously been made at Littleworth Cross, near Farnham, by Henry A. Mangles (d. 1908) and the plants were grown in the greenhouse there by his sister Miss Clara Mangles (d. 1931); several were named, but apparently only ‘Rose Mangles’, with pink flowers, went into commerce.

'Royal Purple'

Flowers about 12 in a compact truss. Corolla widely funnel-shaped, 21⁄2 in. wide, violet-purple with a slight orange flare on a paler ground. Stamen-filaments coloured like the corolla, with purplish anthers. Style crimson, with a dark red stigma. Ovary glabrous, dark chocolate-brown. Leaves dark green, acute. June. A handsome hybrid raised at the Sunningdale Nurseries in Charles Noble’s time. See Rhododendrons at Sunningdale, p. 46.

'Roza Stevenson' ('Roza Harrison')

Flowers 10 to 12 in the truss. Corolla saucer-shaped, mostly seven-lobed, 4 1⁄2 in. wide, pale lemon-yellow, deeper at the centre. Leaves oblong-elliptic, obtuse, about 5 in. long and half as wide. Late April or early May. A lovely hybrid raised by Mr and Mrs Stevenson at Tower Court from Loderi ‘Sir Edmund’ × wardii KW 5736. It received an F.C.C. in 1968, when exhibited by Kew under the name ‘Roza Harrison’. The name commemorates one of the most knowledgeable of rhododendron enthusiasts (d. 1967), who with her husband J. B. Stevenson, built up the famous Tower Court collection of species, much of which was later moved to the Valley Gardens, Windsor Great Park. Eleven years after Mr Stevenson’s death she married Major-General Harrison, but the name given by Kew was altered later to the one she bore when the plant was raised.

Rhododendron 'Roza Stevenson' in the Valley Gardens, Windsor Great Park, UK. 24 April 2020. Image John Anderson.

Rhododendron 'Roza Stevenson' in the Valley Gardens, Windsor Great Park, UK. 24 April 2020. Image John Anderson.

Russautinii (augustinii × russatum)

Flowers in terminal trusses of four or five, sometimes supplemented by trusses from the upper leaf-axils. Corolla 2 in. across, rich near-blue, fading to almost white in the centre, downy in the tube. Stamen-filaments coloured like the corolla, style paler. Calyx well developed, variable in size and form, up to 1⁄4 in. long. Leaves elliptic or oblong-elliptic, 11⁄4 to 2 in. long, obtuse. Late April. This cross was made by Sir John Ramsden before 1936, possibly also in other gardens. The description is made from a particularly fine clone grown at Grayswood Hill, which won a first prize in the Rhododendron Show of 1972 when exhibited from Nymans. In other forms the corollas are speckled and smaller. Russautinii is of erect habit, to about 5 ft.

– ‘Ilam Violet’ is the only clone so far named. It has flowers of a deep violet-purple and was raised by Edgar Stead of New Zealand, using a hybrid he himself raised between R. augustinii and its var. chasmanthum as one parent, and a good form of R. russatum as the other. All the seedlings had pale blue flowers except the one he named ‘Ilam Violet’ (R.Y.B. 1947, p. 47).

The cross between R. augustinii and R. russatum was also made by J. B. Stevenson at Tower Court and named Azamia. For this the good form of R. russatum once known as R. cantabile was used.

Russellianum (arboreum × catawbiense)

Flowers numerous in a dense truss, on downy pedicels about 1 in. long. Corolla campanulate, bright rosy red, unspotted, with darker nectaries. Calyx very small. Leaves thick and leathery, oblong, abruptly acute at the apex, rounded at the base, somewhat convex above from the recurving of the margins, felted beneath, 4 to 9 in. long; petioles 1 in. long, woolly at first, becoming glabrous. This foundation-cross was made by the nurseryman Russell of Battersea and was described and figured by Sweet in 1831 (Brit. Fl. Gard., Vol. I (2nd series), t. 91). It is therefore contemporaneous with Altaclerense (q.v.). The cross was no doubt made in other places, just as the Smithii cross was repeated many times. A clone of Russellianum still in commerce is ‘Southamptonia’, distributed by Rodgers’ Red Lodge Nursery and probably raised there. This agrees well with the original Russellianum except that the flowers are Tyrian Rose with a lighter centre, slightly speckled. The flowers are in trusses of about seventeen and open in April or early May.

The same cross, using a white-flowered form of R. arboreum, was made by Iveson for the Dowager Duchess of Northumberland at Syon House, London, and one form is figured in Bot. Mag., t. 4478 (1849) under the name R. Clivianum. This had white pink-flushed flowers spotted on all the lobes but most densely on the centre lobe.

Rhododendron Russellianum at Tregrehan, Cornwall, UK. 5 April 2014. Image John Anderson.

An enormous mass of Rhododendron Russellianum outside Benmore House in the eponymous Botanic Garden, Argyll, UK. 12 October 2013. Image John Anderson.

Rhododendron Russellianum at Exbury, Hampshire, UK. This is believed to be the clone 'Southamptonia' mentioned in the text. 16 April 2016. Image John Anderson.