Topic summary
Catkins
Extracted from the Wikipedia article Catkin.
Occurrence
In many of these plants, only the male flowers form catkins, and the female flowers are single (hazel, oak), a cone (alder), or other types (mulberry). Corylus jacquemontii has male catkins and also female spikes. In other plants (such as poplar), both male and female flowers are borne in catkins. Populus alba has male catkins which are grey and the female catkins are greyish-green.