Rhododendron decorum – This native of China and Burma bears open trusses of fragrant white to pale pink flowers with a greenish-yellow throat from April to May. It is an RHS Award of Garden Merit winner and tolerates neutral to acidic soils. This species eventually forms a large shrub to small tree and prefers partial shade. Grows 6-7′ high in 10 years. Zone 6.
Rhododendron racemosum – The flower colour of this species rhododendron (native to subalpine regions of China) is quite variable, ranging from white to shell pink and rose. Introduced to the west by Delavay in 1889, it blooms from March to early April and prefers partial shade, with a site sheltered from cold winter winds. Height is also variable, from 3 to 8′. Hardy to zone 7.
Rhododendron sanguineum ssp. sanguineum – Another highly variable species as far as flower colour is concerned, with very fleshy bell-shaped flowers (from March to May) of deep crimson to red being the norm (other flower colours do exist). This native of China has smooth green foliage, with light silvery indumentum on the reverse. Grows 5′ high. Hardy to zone 7.
Rhododendron fulvum – This RHS Award of Garden Merit winner bears beautifully formed trusses of appleblossom-coloured flowers emerging from deep pink buds from March to April. The large deep green leaves also have attractive orange-brown indumentum on the reverse. Eventually forming a large bush or small tree, it prefers partial shade. Grows to 15′ high by 10′ wide. Zone 7.
Rhododendron keiskei – Named after the Japanese botanist Ito Keisuke (1803-1900), this species has been used in the breeding of many significant rhododendrons, including ‘Patty Bee’, ‘Shamrock’ and ‘Mary Flemming’. Native to mountainous regions of Japan, it is quite variable in its growth habit, ranging from 12″ (‘Yaku Fairy’) up to 8′ in height. Hardy to zone 6.