Acatkin orament is a slim, cylindricalflower cluster (aspike), with inconspicuous or nopetals, usuallywind-pollinated (anemophilous) but sometimes insect-pollinated (as inSalix). It contains many, usuallyunisexual flowers, arranged closely along a central stem that is often drooping. Catkins are found in manyplant families, includingBetulaceae,Fagaceae,Moraceae, andSalicaceae.
Catkin-bearing plants include manytrees orshrubs such asbirch,willow,aspen,hickory,sweet chestnut, andsweetfern (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).Corylus jacquemontii has male catkins and also female spikes.[1]In other plants (such aspoplar), both male and female flowers are borne in catkins.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 asclimate change 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.[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 keysynapomorphy among the proposedHamamelididae, also known as Amentiferae (i.e., literally plantsbearing aments). Based onmolecular phylogeny work, it is now believed that Hamamelididae is apolyphyletic group.[5][6] This suggests that the catkin flower arrangement has arisen at least twice independently byconvergent evolution, inFagales and inSalicaceae.[7] Such a convergent evolution raises questions about what theancestral inflorescence characters might be and how catkins did evolve in these two lineages.
The wordcatkin is aloanword from theMiddle Dutchkatteken, meaning "kitten" (compare alsoGermanKätzchen). 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 theLatinamentum, meaning "thong" or "strap".[10]
