The Leaves of Rhododendrons
Most rhododendrons are evergreen. Only the deciduous azaleas and some Arctic and Alpine rhododendron species lose their leaves in winter or early spring. The Japanese azaleas lose only some of their foliage.
The shapes and sizes of leaves show a huge range of variations, from narrow, spear-shaped leaves to almost completely round leaves, in sizes ranging from barely a centimetre (less than 2in) (R. intricatum) to 1m (40 in) long in one subtropical species.
The colour of the leaves also demonstrates an astonishing array of possibilities, particularly among the new shoots in spring. R. williamsianum and its hybrids, for example, produce red or copper-coloured shoots, while R. yakushimanum has conspicuous young shoots that are covered in white, felty hairs. Many azaleas produce breath-takingly beautiful colours in autumn, ranging from wine red to orange-yellow.
The leaves of rhododendrons are like calling cards for the botanist. The shape, size and, in particular, any hairiness or scales on the undersides of the leaves give points of reference when determining the species.