Corylus avellana, The Hazel Tree

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.

Hazel Catkins (Corylus avellana)(Catkins in November)

Hazel Catkins (Corylus avellana)(February)

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).

Hazel Catkins (Corylus avellana)

Hazel Catkins (Corylus avellana)

Hazel Catkins (Corylus avellana)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.

Hazel Catkins (Corylus avellana) Hazel Catkins (Corylus avellana)   Hazel Catkins (Corylus avellana)   Hazel Catkins (Corylus avellana)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.

Hazel flowers, male and female (Corylus avellana)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.

Hazel flowers, female (Corylus avellana)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.

Hazel flowers, female (Corylus avellana) Hazel flowers, female (Corylus avellana)   Hazel flowers, female (Corylus avellana)   Hazel flowers, female (Corylus avellana)Once pollinated the female flowers produce the fruit.

Hazel nuts in July.

Hazelnut fruit (Corylus avellana)Unripened Hazel nuts are white and appear either singly or in small clusters. They are surrounded by a leafy, green sheath called an involucre.

Hazelnut fruit (Corylus avellana)

Hazelnut fruit (Corylus avellana) Hazelnut fruit (Corylus avellana)   Hazelnut fruit (Corylus avellana)   Hazelnut fruit (Corylus avellana)The fruit begins to ripen and turns brown in August.

Hazelnut fruit (Corylus avellana)Note that in this next picture, taken on the twentieth of August, next year’s catkins are already growing on the tree.

Hazelnut fruit (Corylus avellana)In December a few nuts remain.

Hazelnut fruit (Corylus avellana)Now the trees are characterised by the dried involucres that stay on the tree long after the nuts have gone.

Hazelnut involucre (Corylus avellana)

Hazelnut involucre (Corylus avellana)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

Hazel leaf bud (Corylus avellana)

Hazel female flowers (Corylus avellana)

Hazel Catkins (Corylus avellana)Taxonomy:

Kingdom: Plantae

Order: Fagales

Family: Betulaceae

Genus: Corylus

Species: Corylus avellana

Hazelnut fruit (Corylus avellana)

Hazelnut fruit (Corylus avellana)

Hazel (Corylus avellana)Back to Green Wildflowers

Back to Red Wildflowers

Back to the start




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