Rhododendron

On windblown mountain tops grows a small evergreen shrub, the perfectly hemispherical yak rhododendron, with oval leaves densely felted on their undersides. When the thick snows finally thaw in June, the pale rose-red flower buds open, soon turning white or near-white. After flowering new foliage appears, covered in thick white or cream coloured felt which gradually disappears from the upper surfaces to reveal the dark green shiny leaves. On the undersides the felt persists, changing gradually to a darker brown.

The small island of Yakushima lies about 120 km south of Kyushu, off the southern tip of Japan. The highest point on the island rises to 1935m asl (= above sea level), and this is where the smallest and hardiest yak rhododendrons are found.

The first yak rhododendrons seen in Europe were three specimens sent in 1934 by the Japanese botanist Koichiro Wada to Lionel de Rothschild in England. Two of them survived and became the basis for the successful spread of the species throughout Europe and the USA. Several good forms have been named and the species has been the object of enthusiastic breeding, aimed at producing suitable cold, wind and sun hardy rhododendrons for the small modern garden.

The first yak rhododendrons were planted at Mustila at the change of the decade 1980s–1990s. The shrubs have thrived, flowering beautifully and regularly when the winters aren’t too severe and snow cover has been sufficient. The silvery new foliage appears after flowering, in late June, and is as impressive in its way as the flowering.

The pink shell azalea grows naturally in the forests of North Carolina in the USA. When it flowers in May on the bare branches it looks as if a cloud of beautiful butterflies has landed to greet the arrival of summer. The blossoms are mainly in shades of pale pink, though some white varieties have been selected and named.

Exceptionally among the hundreds of natural Rhododendron species, the pink shell azalea is one of the very few that refuses to cross with other members of the genus. Not that it needs to be improved by crossing; its slender beauty is in a class of its own. The pink shell belongs to the Rhodora section, whose only other species is R. canadense (English common name: rhodora), but they are not closely related.

The pink shell suits woodland gardens perfectly in combination with similar plants such as rhodora, Chinese Alprose (R. dauricum), or the Korean R. mucronulatum. In fact, it deserves a place in every woodland garden; it needs little care and is in an untamed way one of the very best of the genus.

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.