Hazel catkins are an inflorescence of small flowers that form in the autumn and are with us all winter, they can begin to open in January if the weather is mild.
(Catkins in November)
Each catkin is a flower head, comprised of about 240 small flowers. Each flower is covered by a triangular downy bract, beneath the bract are four stamens and each stamen has two yellow anthers (the pollen producing male part of a flower).
A single anther will produce around nine thousand grains of pollen and one catkin, nearly nine million. A Hazel tree produces a lot of pollen.
Hazel is wind-pollinated and not reliant on insects so most of the pollen produced is blown away and doesn’t find it’s target.
The target for the pollen is the style of the female flower.
The Hazel tree is monoecious, meaning that each tree has both male and female flowers. The female flowers grow in clusters from small buds above the catkins. Only the red styles of the flowers protrude from the buds and the female inflorescence typically measures 2-4 mm across, It is a very small flower.
Despite anything that you may read to the contrary (or that I may have told you in the past) the location and timing of the female flowers has nothing to do with avoiding self pollination. Corylus avellana is self incompatible, it cannot self-fertilise.
Each female flower has two red styles (The pollen receiving female part of a flower). Each bud contains a cluster of between four and fourteen female flowers. Only the styles emerge from the bud.
Once pollinated the female flowers produce the fruit.
Hazel nuts in July.
Unripened Hazel nuts are white and appear either singly or in small clusters. They are surrounded by a leafy, green sheath called an involucre.
The fruit begins to ripen and turns brown in August.
Note that in this next picture, taken on the twentieth of August, next year’s catkins are already growing on the tree.
In December a few nuts remain.
Now the trees are characterised by the dried involucres that stay on the tree long after the nuts have gone.
There is a mass of misinformation on the internet. I used the following sources to verify the accuracy of my post.
Acta Agrobotanica Vol. 61 (1) 33-39 2008
Molecular Biology Reports April 2012 Vol. 39 Issue 4 pp 4997-5008
Species: Corylus avellana
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