The Catkin (also called Kitten for the shape similar to the tail of a cat) is a spike-shaped unisexual inflorescence, usually pendulous, with a flexible stem and with sessile and pet-free flowers or with reduced flowering envelopes, anemophilous pollination. .
The catkins are either masculine, more elongated, or feminine. The male catkins are reduced to the stamens while the female ones to the stigma.
It is a characteristic inflorescence of certain trees, especially the suborder Hamamelidae, the families Salicaceae and Fagaceae. In these classes of plants, the pollination is anemophilous, that is to say that the transport of pollen, very abundant, comes to be realized through the wind. The cat can be simple (Populus, Salix), compound, when the main axis has short ramifications (Junglas), globulose (Platanus), ovoid (Alnus), interrupted (many Quecus).
The flowering age of the catkins is spring and generally appear before the leaves. The pollen of some of these can be, for the human species, an allergy source.