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 ). They contain many, usually unisexual flowers, arranged closely along a central stem that is often drooping. They are found in many plant families, including Betulaceae, Fagaceae, Moraceae, and Salicaceae.
Catkin-bearing plants include many trees or shrubs such as birch, willow, aspen, hickory, sweet chestnut, and sweetfern (Comptonia).[ citation needed ]
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). Such as Corylus jacquemontii has male catkins and also female spikes. [1] In other plants (such as poplar), both male and female flowers are borne in catkins. Such as Populus alba has male catkins which are grey and the female catkins are greyish-green. [2]
While the blooming months for catkins may vary due to factors such as climate change, 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. [3]
In Britain, catkins can be seen in January or February, when many trees are bare for winter. They can even occur in December. [4]
For some time, catkins were believed to be a key synapomorphy 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 group. [5] [6] This suggests that the catkin flower arrangement has arisen at least twice independently by convergent evolution, in Fagales and in Salicaceae. [7] Such a convergent evolution raises questions about what the ancestral inflorescence characters might be and how catkins did evolve in these two lineages.
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. [8] [9] Ament is from the Latin amentum, meaning "thong" or "strap". [10]
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 the temperate Northern Hemisphere, with a few species reaching the Southern Hemisphere in the Andes in South America. Their typical flowers are catkins and often appear before leaves.
A raceme or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the shoot grows in height, with no predetermined growth limit. Examples of racemes occur on mustard, radish, and orchid plants.
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, though some botanists split the hazels into a separate family Corylaceae. The fruit of the hazel is the hazelnut.
Corylus avellana, the common hazel, is a species of flowering plant in the birch family Betulaceae, native to Europe and Western Asia. It is an important component of the hedgerows that were, historically, used as property and field boundaries in lowland England. The wood was traditionally grown as coppice, with the poles cut being used for wattle-and-daub building, and agricultural fencing.
Salix × fragilis, with the common names crack willow and brittle willow, is a hybrid species of willow native to Europe and Western Asia. It is native to riparian habitats, usually found growing beside rivers and streams, and in marshes and water meadow channels. It is a hybrid between Salix euxina and Salix alba, and is very variable, with forms linking both parents.
Corylus maxima, the filbert, is a species of hazel in the birch family Betulaceae, native to southeastern Europe and southwestern Asia, from the Balkans to Ordu in Turkey.
Salix babylonica is a species of willow native to dry areas of northern China, but cultivated for millennia elsewhere in Asia, being traded along the Silk Road to southwest Asia and Europe.
The grey dagger is a moth of the family Noctuidae.
Salix magnifica is a species of willow in the family Salicaceae. It is endemic to Sichuan in southwestern China, where it grows at high altitudes of 2,100–3,000 m above sea level. It is threatened by habitat loss.
Corylus heterophylla, the Asian hazel, is a species of hazel native to eastern Asia in northern and central China, Korea, Japan, and southeastern Siberia.
Coleophora anatipennella is a moth of the case-bearer family (Coleophoridae).
Epione vespertaria, the dark bordered beauty, is a moth of the family Geometridae.
Salix arbusculoides is a species of flowering plant in the willow family known by the common name little tree willow. It is native to northern North America, where its distribution extends across Alaska and most of Canada.
Salix richardsonii is a species of flowering plant in the Salicaceae, or willow family. It is known by the common names Richardson's willow and woolly willow. It is native to Russia and northern North America, where it occurs in Alaska and northern Canada. Some authorities consider it to be a subspecies, Salix lanata subsp. richardsonii(Hook.) A. K. Skvortsov rather than a species itself.
Salix petrophila, commonly known as alpine willow and Rocky Mountain willow, is a Northwest American mountain shrub in the willow family (Salicaceae).
Salix argyracea is a large shrub from the genus of willow (Salix) with up to 10 centimeters long leaf blades with a felty hairy and shiny underside. The natural range of the species is in Kazakhstan, Kyrgyzstan, and China.
Salix eriostachya is a species from the genus of willows (Salix) and grows as a shrub. The leaf blades are 4 to 11 centimeters long. The natural range of the species is in India, Nepal, and China.
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