Rhododendron Cultivars I

Ibex (griersonianum × pocophorum)

Similar to May Day and no better. It possibly grows taller, however.

Rhododendron Ibex at Exbury, Hampshire, UK under Lionel de Rothschild's number LR 1011. 25 April 2013. Image John Anderson.

'Icecream'

Flowers 12 to 14 in a dome-shaped truss. Corolla funnel-shaped, 31⁄2 in. or slightly more wide, light pink with a white throat, spotted with olive on the upper lobe. Compact habit. Late May or early June (Slocock). A.M.T. June 2, 1960. It is the result of a complex cross involving three species – R. dichroanthum, R. decorum, and R. discolor – and a Hardy Hybrid.

Idealist (Naomi × wardii)

Flowers about 12 in the truss on purplish pedicels 2 in. long. Corolla saucer-shaped, 4 in. wide, 5– to 7-lobed even in the same truss, buff-pink in the bud, opening pale primrose, with a pinkish flush at first, and with two bands of light red streaking below the upper lobes. Leaves oblong elliptic, to about 5 in. long, half as wide, broadly obtuse at the apex; petioles stained purple. Medium size. May. (Rothschild. A.M. 1945.) The description is made from a commercial clone. A lovely hybrid, related to the Carita grex, but with a shape of flower inherited from R. wardii.

The cross was later repeated at Exbury and some of the seedlings were sent to the Knap Hill nursery, from which ‘Vienna’ was selected and registered in 1962.

Rhododendron 'Idealist' at Arboretum Wespelaar, Belgium. 11 April 2024. Image Tom Christian.

Close-up on the large flowers of Rhododendron 'Idealist' at Exbury, Hampshire, UK. 6 May 2014. Image John Anderson.

Rhododendron 'Idealist' at the Savill Garden, Windsor Great Park, UK. 10 May 2012. Image John Anderson.

Rhododendron 'Idealist' at Arboretum Wespelaar, Belgium. 11 April 2024. Image Tom Christian.

'Ilam Violet'

‘Ilam Violet’ is the only clone so far named from the Russautinii group. 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).

'Ima-shojo'

Corolla 7⁄8 in. wide, deep red (Turkey Red); anthers pale, conspicuous. Calyx-segments mostly petaloid, but short and narrow, so the flower is not hose-in-hose. Leaves dark green and glossy, unusually short, even the spring leaves being mostly 3⁄4 in. or less long. Very dense habit (Kurume; Wilson No. 36).

Impeanum (hanceanum × impeditum (fastigiatum?))

Flowers about five in each inflorescence. Corolla rotate, about 11⁄4 in. wide, ‘beautiful deep lilac’ in the F.C.C. plant, but paler in some plants. Leaves dark green, glaucous beneath, elliptic or oblong-ovate, to 3⁄4 in. long. A densely branched, low-growing shrub. May. (Kew; introduced 1932. F.C.C. 1934.) Useful for its late flowering. It is almost certain that R. fastigiatum was used, not R. impeditum.

Impi (sanguineum subsp. didymum × 'Moser's Maroon')

Flowers 10 to 12 in small trusses; pedicels dark red, white-hairy. Corolla funnel-shaped, 2 1⁄4 in. wide, deep vinous red (brilliant red in transmitted light). Anthers dark red. Medium growth, erect habit. June. (Rothschild. A.M. 1945.)

Rhododendron Impi at Exbury, Hampshire, UK. 20 June 2008. Image John Anderson.

Rhododendron Impi at Exbury, Hampshire, UK. 3 July 2013. Image John Anderson.

Inamorata (discolor × wardii)

Flowers about eight in a lax truss on plum-coloured pedicels. Corolla suphur-yellow, bowl-shaped, about 3 in. wide, with a red mark at the base. A vigorous hybrid taking after R. discolor in its foliage and late-flowering (June) and after R. wardii in its flowers. It was raised by Lionel de Rothschild at Exbury and received an Award of Merit on June 27, 1950, but its normal flowering time is early in the month.

Rhododendron Inamorata at Exbury, Hampshire, UK. 14 June 2008. Image John Anderson.

Intrifast (fastigiatum × intricatum)

This hybrid is really so near to R. fastigiatum that for garden purposes it could be regarded as a good form of it, with exceptionally blue young foliage. It is of dense mounded habit, to about 2 ft. (Lowinsky.)

'Irene Koster'

White, flushed crimson pink, but the central lobe almost white, with a yellow flare, 21⁄4 in. wide; tube crimson pink. Very fragrant (Occidentale Hybrid; Koster and Co.). According to H. J. Grootendorst, seedlings were originally distributed under this name.

Rhododendron 'Irene Koster' at Cherry Tree Arboretum, Shropshire, UK. 11 May 2023. Image Tom Christian.

Rhododendron 'Irene Koster' at Cherry Tree Arboretum, Shropshire, UK. 11 May 2023. Image Tom Christian.

Rhododendron 'Irene Koster' (RHS Rosemoor, Devon, UK; 28 May 2021). Image Julian Sutton.

Rhododendron 'Irene Koster' (RHS Rosemoor, Devon, UK; 28 May 2021). Image Julian Sutton.

'Irohayama'

Corolla mauvish pink at the edge, white in the throat, unspeckled or almost so, about 11⁄2 in. wide. Style and filaments white. Calyx normal. Dense habit, up to 5 ft (Kurume; Wilson No. 8). A.M. 1952.

'Isabella Mangles'

Flowers about 12 in the truss on pedicels to 21⁄4 in. long. Corolla campanulate, with a short, broad tube and spreading limb, about 4 in. wide, slightly wavy at the edge, rosy pink, paling towards the centre of the lobes and deeper outside, becoming creamy white before it falls. Leaves oblong-elliptic, to 61⁄2 by 23⁄4 in. Early May. This is one of the finest creations of J. H. Mangles and doubtless the result of crossing R. griffithianum with some hardy hybrid. It grows and flowers well at Kew, where there are plants 10–12 ft high, but is uncommon outside collections.

'Ivery's Scarlet'

Flowers 12 to 14 in a dense truss. Calyx very small, glandular. Corolla campanulate, 21⁄2 in. wide, deep vivid red, speckled on the three upper lobes. Leaves narrowly oblong-elliptic, tapered at both ends, rich green above, underside paler, dull green, with a prominent midrib. Slender habit, to about 15 ft. May. A very handsome hybrid from blood-red R. arboreum, gaining its late flowering and hardiness from, probably, R. ponticum. It was raised at the middle of the last century by the nurseryman Ivery of Dorking. Millais, who much admired it, gives its subsequent history in his Rhododendrons, p. 120. It needs a sheltered place, but is quite hardy and flowers over a long period. Most large collections have it, but it is scarce in commerce.