Type in the word "rhododendron" in an image search, and countless beautiful photos of vibrantly-coloured blooms will appear. The same is true when searching through the Botany Photo of the Day archives: Rhododendron 'Cornubia', Rhododendron moupinense, and Rhododendron periclymenoides represent but a few of the beautiful rhododendron flowers that we have featured.
UBC Botanical Garden has a fabulous collection of rhododendrons from Asia and North America. Like many of our visitors, I am amazed at the beauty and diversity of flower forms possessed by this remarkable genus. As I wander the narrow, shaded pathways of the David C. Lam Asian Garden, however, I am just as often struck by the beauty of the rhododendron leaves that I encounter and by the way that these leaves play with the Garden's ambiance. The thick, substantial rhododendron leaves allow brief shafts of light through the canopy, shining a spotlight on random botanical objects that would otherwise pass unnoticed: here, a spot of light touches on the threads of last-year's maple leaf; there, a tiny tip of a pipevine corkscrews brightly against a dark background. Tiny botanical beauties go unnoticed against a wall of fuchsia flowers, but shine against the restrained backdrop of rhododendron leaves.
Of rhododendron leaves, I find those with contrasting indumentum the most captivating. Indumentum is the coating of extremely fine hairs that can be found on the lower surface of the leaves of many rhododendron species, including those of Rhododendron falconeri. Today's photo shows the underside of one of these leaves, which in its entirety measures about 20 cm long and 8 cm wide, is elliptic in shape, and is held on a long petiole (stalk). I am entranced by the pinnate pattern formed by this leaf's strong veins and by the dusting of felt-like, rusty hairs.
The upper surfaces of Rhododendron falconeri leaves are dark green and have been described as curiously wrinkled. A very light coating of hairs, termed tomentum, coats these surfaces and may prevent insect herbivory.