Catkin
A catkin is a slim flower cluster (a "spike") that is usually wind-pollinated but sometimes insect-pollinated. It has many flowers arranged closely along a drooping central stem.[1] Usually, it is unisexual.
It is found in many plant families, including Betulaceae, Fagaceae, Moraceae, and Salicaceae. The catkin flower arrangement has arisen at least twice independently by convergent evolution in Fagales and Salicaceae.