Rhododendron ludlowii Cowan

This is a distinctive species that is rare in the wild. Royal Horticultural Society (1997).

From Bean’s Trees and Shrubs:

R ludlowii Cowan

Allied to R. pumilum and of similar dwarf habit, but differing most markedly in its yellow flowers, spotted with reddish brown inside. The calyx is larger than in R. pumilum and leafy, and a further point of distinction is that the obovate leaves are faintly crenated at the edge. It was discovered by Ludlow and Sherriff in 1936 on the Lo La, a pass at 13,500 ft on the border between Tibet and Assam, near the source of the Siyom river, a tributary of the Brahmaputra. Two years later, they and George Taylor collected seeds a short way to the north, on Tsari Sama, Tibet, and from these the cultivated plants derive. Bot. Mag., n.s., t. 412.R. ludlowii is not an easy plant to cultivate successfully. But Mr R. B. Cooke, who supplied the flowering piece figured in the Botanical Magazine, grew it successfully in Northumberland in a raised bed on the north side of a hedge, where it is screened from the sun for about six hours in the middle of the day. It is slow-growing, but bears flowers when the plant is still not much larger than its own corolla. Perhaps this rhododendron’s chief claim to distinction is that it is a parent of the lovely ‘Chikor’ and ‘Curlew’, described in the section on hybrids.