Of the four evergreen rhododendrons native to the Caucasus Mountains, Ungern’s rhododendron (R. ungernii) is both the least cultivated and the least known. To some extent it resembles the Smirnow rhododendron (R. smirnowii), both species having leaves with felted undersurfaces. However, the upper surface on the Ungern loses its hairiness very quickly when the leaves reach full size, while with the Smirnow a degree of hairiness persists. In the wild the Ungern reaches up to 6 metres high, and its greatest value in cultivation lies in the late flowering and the large leaves, up to 20 cms. The flower buds are pink, but the flowers open white.
It seems that true Ungern’s rhododendron is not cultivated anywhere in Scandinavia. It is winter tender and also has a reputation for being otherwise difficult to grow; there is a saying that a true R. ungernii is recognisable by being dead. Mustila obtained some R. ungernii plants from Metla (Finnish Forest Research Centre) in the 1970s, and all the true species died quickly. The only surviving plant was a hybrid. It is still alive, growing at the foot of Serbian spruce near Kenkäkallio (Shoe Rock), but unfortunately has never flowered.