The is more correctly Rhododendron arboreum subsp. cinnamomeum var. roseum

This rhododendron is sometimes listed as Rhododendron arboreum subsp. cinnamomeum var. roseum. The species (R. arboreum) (national flower of Nepal) is widely distributed in the wild for example in China, India, Pakistan, Thailand. It typically forms a small tree of some 12m height, as in Belfast Botanic Gardens, where it has considerable maturity. It can be seen in a prominent position on the grass to the right-hand end of the stove wing of the Palm House. It flowers early to mid-season (photos below taken in mid-April) with 15 to 20 bell-shaped flowers in a cluster. The leaves are pointed in shape and have a thin dusting of brown hairs, the indumentum, on the underside.

Photos taken in Belfast Botanic Gardens in April 2021. Copyright: Friends of Belfast Botanic Gardens.