Note the difference in the leaves on these two plants. The common and well-known leaf shape of evergreen rhododendrons is oblong-lanceolate to ovate, as you can see on Rhododendron ‘Caucasicum Pictum’ – facing the bushes on the left. The specimen growing on the right, Rhododendron williamsianum, has a distinctly broadly elliptic and heart-shaped leaf base at the petiole, unlike the previous one.