A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind- pollinated ( anemophilous) but sometimes insect-pollinated (as in '' Salix''). It contains many, usually unisexual flowers, arranged closely along a central stem that is often drooping. Catkins are found in many

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

families, including Betulaceae, Fagaceae, Moraceae, and Salicaceae.

Occurrence

Catkin-bearing plants include many trees or shrubs such as birch, willow, aspen,

hickory Hickory is a common name for trees composing the genus ''Carya'', which includes 19 species accepted by ''Plants of the World Online''. Seven species are native to southeast Asia in China, Indochina, and northeastern India (Assam), and twelve ...

, sweet chestnut, and sweetfern (''Comptonia''). 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. While the blooming months for catkins may vary due to factors such as

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

and latitude, the following are some general timeframes: Hazel catkins bloom from January to March, alder catkins from February to March, silver birch catkins from March to May, oak catkins from April to May, and white willow catkins from April to May. In Britain, catkins can be seen in January or February, when many trees are bare for winter. They can even occur in December.

Evolution

For some time, catkins were believed to be a key

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...

among the proposed Hamamelididae, also known as Amentiferae (i.e., literally plants ''bearing aments''). Based on molecular phylogeny work, it is now believed that Hamamelididae is a

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

group. Savolainen, V., M. W. Chase, S. B. Hoot, C. M. Morton, D. E. Soltis, C. Bayer, M. F. Fay, A. Y. De Bruijn, S. Sullivan, and Y.-L. Qiu. 2000. Phylogenetics of flowering plants based on combined analysis of plastid ''atpB'' and ''rbcL'' gene sequences. Systematic Biology 49:306-362.Soltis, D. E. et alii. (28 authors). 2011. "Angiosperm phylogeny: 17 genes, 640 taxa". ''American Journal of Botany'' 98(4):704-730. This suggests that the catkin flower arrangement has arisen at least twice independently by

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

, in Fagales and in Salicaceae.Cronk Q. C. B., Needham I., and Rudall P. J. 2015. Evolution of catkins: inflorescence morphology of selected Salicaceae in an evolutionary and developmental context. ''Frontiers in Plant Science''. 2015; 6: 1030. Such a convergent evolution raises questions about what the ancestral inflorescence characters might be and how catkins did evolve in these two lineages.

Etymology

The word ''catkin'' is a loanword from the Middle Dutch ''katteken'', meaning " kitten" (compare also German ''Kätzchen''). This name is due either to the resemblance of the lengthy sorts of catkins to a kitten's tail, or to the fine fur found on some catkins. ''Ament'' is from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''amentum'', meaning "thong" or "strap".

Gallery

Fagales"> File:Ostrya carpinifolia in Italy male catkins.jpg , Male catkins of hop-hornbeam ('' Ostrya carpinifolia'') File:Catkins Corylus avellana-Mont Bart-5124~2015 12 26.JPG , Young male catkins of hazel ('' Corylus avellana'') File:P3240141.JPG , Mature male catkins of hazel ('' Corylus avellana'') Salicaceae"> File:Young-catkin.jpg , Young male catkin of a willow ('' Salix'' sp.) File:Willow catkin 2 aka.jpg , Three male catkins on a willow ('' Salix'' sp.) File:Salix female catkin.jpg , Female flowering catkin on a willow ('' Salix'' sp.)

References

{{Authority control Plant morphology