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Rhododendron Cultivars O

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Sponsor

Kindly sponsored by
Peter Norris, enabling the use of The Rhododendron Handbook 1998

Credits

New article for Trees and Shrubs Online.

Recommended citation
'Rhododendron Cultivars O' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-cultivars-o/). Accessed 2026-05-13.

Family

  • Ericaceae

Genus

Other taxa in genus

Glossary

References

There are no active references in this article.

Credits

New article for Trees and Shrubs Online.

Recommended citation
'Rhododendron Cultivars O' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-cultivars-o/). Accessed 2026-05-13.

Editorial Note

Entries here are derived, unchanged, from Bean’s articles on Rhododendron hybrids, which, as transcribed into Trees and Shrubs Online format, were unsearchable. These entries, from his sections on “Rhododendron hybrids”, “Deciduous azaleas” and “Evergreen azaleas”, have been extracted and given their own entry under a series of pages Rhododendron Cultivars A, B, etc. Each cultivar’s affiliation to the above categories is noted.

Hybrid rhododendrons follow an unconventional form of nomenclature. All progeny of a stated cross form what was formerly called a grex, now called a Group, and share the same grex/Group name, which is not given inverted commas. For example, all progeny from the cross R. decorum subsp. diaprepes × R. auriculatum are in the Polar Bear Group, and all from any cross between Rhododendron Aurora Group and Rhododendron griffithianum are referred to Yvonne Group, regardless of when or by whom the cross was made. Within the Group individual clones may be recognised as cultivars, being identified by the use of single inverted commas in the usual way: Rhododendron Polar Bear Group ‘Polar Bear’, or Rhododendron Yvonne Group ’ Yvonne Pride’. Reference to the the International Rhododendron Register and Checklist, produced by the Royal Horticultural Society, is advised. A digital version is available through the good offices of the RHS Rhododendron, Camellia and Magnolia Group.

The cultivars presented here represent a fraction of the total diversity of Rhododendron cultivars, comprehensively covered by the Register. The listing on TSO will be developed further when funding permits.

'Old Port'

Elepidote rhododendron

Flowers about 15 in the truss. Corolla widely funnel-shaped, about 2 1⁄2 in. across, dull wine-red with blackish crimson markings. Style and stamen-filaments crimson. Calyx very small. Leaves glossy, shaped more or less as in R. catawbiense, of which it is a hybrid. Medium size, dense habit. Mid-June. (Waterer, Knap Hill, before 1865.)

Rhododendron Cultivars O 'Old Port'

Rhododendron 'Old Port' in the Valley Gardens, Windsor Great Park, UK. 8 May 2017. Image John Anderson.

Rhododendron Cultivars O 'Old Port'

Rhododendron 'Old Port' in the Valley Gardens, Windsor Great Park, UK. 25 May 2021. Image John Anderson.

'Oomurasaki'

Evergreen azalea

With large, rosy purple flowers heavily spotted on the upper lobes (R. pulchrum var. calycinum (Lindl.) Rehd.). This was introduced by Fortune from China, and again later from Japan, but is apparently not in commerce at the present time.

'Orange Beauty'

Evergreen azalea

Corolla 11⁄2 to 13⁄4 in. wide, slightly frilled, soft scarlet (43c), speckled on the upper lobes. Leaves glossy, light green. Low bushy habit, rarely more than 3 ft high but more in width. Late April or early May (R. kaempferi × ‘Hinodegiri’; C. B. van Nes). F.C.C.T. 1958. A well-known and valuable azalea, flowering unfailingly. It is best in slight shade as the flowers fade rather quickly in hot sunny weather.

Oreocinn (cinnabarinum × oreotrephes)

Lepidote rhododendron

Flowers about seven in a loose truss. Corolla tubular-campanulate 11⁄2 to 2 in. wide, lilac pink with two lines of brown markings. An attractive hybrid raised by E. J. P. Magor before 1919, the year it first flowered. It flowers freely in May and grows to about 10 ft.

Magor also crossed R. cinnabarinum with R. yunnanense (Yunncinn grex). He judged the result to be inferior to Oreocinn, but the Yunncinn cross was repeated at Bodnant and produced the clone ‘Youthful Sin’, which received an Award of Merit in 1960.

'Oudijk's Sensation'

Elepidote rhododendron

Flowers five to seven in the truss. Corolla funnel-campanulate, 3 in. wide, undulated at the margin, Rose Bengal, darker in the bud and on the reverse, speckled with crimson on the lower part of the upper lobe. Leaves oblong-elliptic, to about 4 in. long and half as wide, with a pronounced cusp at the apex; petiole dark red. An attractive hybrid of recent introduction, flowering in May. It belongs to the Nordeney grex (‘Essex Scarlet’ × williamsianum), raised by Dietrich Hobbie, and was put into commerce by Le Feber and Co.

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