The leaves of the oleaster (Elaeagnus sp.) shrubs in my garden are glossy green above and dazzling white below. The cause of the highly reflective undersurface is revealed under the microscope – thousands of overlapping, flattened hairs, shaped like multi-armed starfish. Each is about a fifth of a millimetre in diameter and attached to the leaf surface by a short stalk. Imagine a surface covered in vast numbers of overlapping, flat, open umbrellas and you’ll have a pretty accurate mental picture of how they’re arranged. The hairs prevent excess water loss from the pores (stomata) on the leaf undersurface, while allowing free passage to the all-important carbon dioxide that the leaf needs for photosynthesis.