Rhododendron caloxanthum Balf. f. & Farrer

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Credits

Article from Bean's Trees and Shrubs Hardy in the British Isles

Recommended citation
'Rhododendron caloxanthum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-caloxanthum/). Accessed 2020-08-07.

Genus

Infraspecifics

Other species in genus

Glossary

calyx
(pl. calyces) Outer whorl of the perianth. Composed of several sepals.
corolla
The inner whorl of the perianth. Composed of free or united petals often showy.
bud
Immature shoot protected by scales that develops into leaves and/or flowers.
glabrous
Lacking hairs smooth. glabrescent Becoming hairless.
glandular
Bearing glands.
glaucous
Grey-blue often from superficial layer of wax (bloom).
ovary
Lowest part of the carpel containing the ovules; later developing into the fruit.
subspecies
(subsp.) Taxonomic rank for a group of organisms showing the principal characters of a species but with significant definable morphological differentiation. A subspecies occurs in populations that can occupy a distinct geographical range or habitat.
synonym
(syn.) (botanical) An alternative or former name for a taxon usually considered to be invalid (often given in brackets). Synonyms arise when a taxon has been described more than once (the prior name usually being the one accepted as correct) or if an article of the International Code of Botanical Nomenclature has been contravened requiring the publishing of a new name. Developments in taxonomic thought may be reflected in an increasing list of synonyms as generic or specific concepts change over time.

References

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Credits

Article from Bean's Trees and Shrubs Hardy in the British Isles

Recommended citation
'Rhododendron caloxanthum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-caloxanthum/). Accessed 2020-08-07.

An evergreen shrub 3 to 5 ft high; young shoots glandular. Leaves broadly oval to roundish, 112 to 212 in. long, not quite so wide, pale glaucous green beneath, glabrous or nearly so at maturity; stalk about 12 in. long, glandular. Flowers in trusses of four to nine opening in April and May. Corolla bell-shaped, 134 in. wide, scarcely so long, five-lobed, scarlet in bud, sulphur- to orange-yellow when fully open; stamens ten, up to 1 in. long, not downy; ovary densely furnished with stalked glands which extend to the lower third of the pistil. Calyx small and like the flower-stalk (which is about 12 in. long) thickly clad with glands. (s. Thomsonii ss. Campylocarpum)

R. caloxanthum was discovered by Farrer and Cox on the Hpimaw and Chimili passes, upper Burma, near the border with China, in 1919 and was introduced from there (Farrer 937). Farrer described the flowers as vermilion in bud, flushed with apricot and tipped with orange-scarlet as they open, finally clear citron yellow. In the following year Farrer found it farther north, on the Chawchi pass, where it is even more abundant, covering the open slopes and precipice ledges in dense masses of 2-3 ft jungle (Cox, Farrer’s Last Journey, pp. 225 and 239).

Plants raised from Farrer 937 agreed well with the wild parents in their flowers and this form received an Award of Merit when shown from Exbury on May 1, 1934. Farrer described the young shoots as ‘almost cobalt blue’, a character which did not show on the plants raised from his seeds, though there are forms of the species in cultivation which have the mature leaves distinctly glaucous. R. caloxanthum is perfectly hardy south of London, in light woodland. It is very closely allied to R. campylocarpum, and according to Cowan and Davidian the two species merge into one another.

From the Supplement (Vol. V)

This becomes a subspecies of R. camplyocarpum, with R. telopeum as a synonym.


R telopeum Balf. f. & Forr

This species really only differs from R. caloxanthum in having on the average rather smaller leaves, up to 2 in. long, 1{5/8} in. wide, and the two should really be united, under the name R. telopeum, which has priority. It was described from a specimen collected by Forrest in Tsarong, S.E. Tibet, at the northern end of the Irrawaddy-Salween divide.

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