A catkin or ament is a slim, cylindrical

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

cluster (a spike), with inconspicuous or no

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

s, usually

wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

pollinated Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or butterflies; bird ...

(

anemophilous Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including grasses, sedges, and rushes. Other common anemophilous pla ...

) but sometimes insect-pollinated (as in ''

Salix Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions. Most species are known ...

''). It contains many, usually

unisexual Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...

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 Betulaceae, the birch family, includes six genera of deciduous nut-bearing trees and shrubs, including the birches, alders, hazels, hornbeams, hazel-hornbeam, and hop-hornbeams, numbering a total of 167 species. They are mostly natives of ...

Fagaceae The Fagaceae (; ) are a family of flowering plants that includes beeches, chestnuts and oaks, and comprises eight genera with around 1,000 or more species. Fagaceae in temperate regions are mostly deciduous, whereas in the tropics, many species ...

Moraceae Moraceae is a family of flowering plants comprising about 48 genera and over 1100 species, and is commonly known as the mulberry or fig family. Most are widespread in tropical and subtropical regions, less so in temperate climates; however, their ...

, and

Salicaceae The Salicaceae are the willow family of flowering plants. The traditional family (Salicaceae ''sensu stricto'') includes the willows, poplars. Genetic studies summarized by the Angiosperm Phylogeny Group (APG) have greatly expanded the circumsc ...

Occurrence

Catkin-bearing plants include many

trees In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only p ...

shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...

s such as

birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' contains 3 ...

willow Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions. Most species are known ...

aspen Aspen is a common name for certain tree species in the Populus sect. Populus, of the ''Populus'' (poplar) genus. Species These species are called aspens: * ''Populus adenopoda'' – Chinese aspen (China, south of ''P. tremula'') * ''Populus da ...

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 Hazels are plants of the genus ''Corylus'' of deciduous trees and large shrubs native to the temperate Northern Hemisphere. The genus is usually placed in the birch family, Betulaceae,Germplasmgobills Information Network''Corylus''Rushforth, K ...

oak An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

), a cone (

alder Alders are trees of the genus ''Alnus'' in the birch family Betulaceae. The genus includes about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species ex ...

), or other types (

mulberry ''Morus'', a genus of flowering plants in the family Moraceae, consists of 19 species of deciduous trees commonly known as mulberries, growing wild and under cultivation in many temperate world regions. Generally, the genus has 64 subordinat ...

). '' 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 ''Populus alba'', commonly called silver poplar,Webb, C. J.; Sykes, W. R.; Garnock-Jones, P. J. 1988: Flora of New Zealand. Vol. IV. Naturalised Pteridophytes, Gymnosperms, Dicotyledons. 4. Christchurch, New Zealand, Botany Division, D.S.I.R. si ...

'' 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 Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

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 The Fagales are an order of flowering plants in the rosid group of dicotyledons, including some of the best-known trees. Well-known members of Fagales include: beeches, chestnuts, oaks, walnut, pecan, hickory, birches, alders, hazels, hornb ...

and in

.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 A loanword (also a loan word, loan-word) is a word at least partly assimilated from one language (the donor language) into another language (the recipient or target language), through the process of borrowing. Borrowing is a metaphorical term t ...

from the

Middle Dutch Middle Dutch is a collective name for a number of closely related West Germanic dialects whose ancestor was Old Dutch. It was spoken and written between 1150 and 1500. Until the advent of Modern Dutch after 1500 or , there was no overarching sta ...

''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".

Occurrence

Evolution

Etymology

Gallery

References