Leaves are covered in a waxy cuticle. The structure and chemistry of the cuticle on the redbud leaves repels water more strongly. As the water is repelled, it pulls away from the leaves and forms an almost spherical ball, which reflects light. The angle between the leaf and the water is the contact angle – the more obtuse the angle, the higher the water stands from the leaf. The oak repels water with less force, leading to a more acute contact angle – more of the water is in contact with the leaf, and the flattened pool of water reflects less 
The droplets of leaves ----> is called DEW ---> are tiny drops of water that form on cool surfaces at night, when atmospheric vapor condenses.