Hazel flowers

The arrival of hazel flowers is one of my favourite sights of spring – in amongst the bare hedgerows, there is something magical about finding a hazel heavy with catkins, as though somebody had been out and hung decorations upon a bare tree in the middle of nowhere.

A tiny female hazel flower in the foreground with the male hazel catkins - an inflorescence containing an average of 240 individual flowers - in the background.
A tiny female hazel flower in the foreground with the male hazel catkins – an inflorescence containing an average of 240 individual flowers – in the background.

The hazel has both male and female flowers on each shrub, and the two flowers are quite different. The male flowers are gathered within the long, breeze-blown catkins and these are by far the most prominent. Each catkin is made up of many individual flowers – these are the small green/yellow male flowers which produce the pollen. There are around 240 male flowers in each catkin and they form during the previous summer so that they are ready to open in the dead of winter and flower through the spring.

The hazel is wind pollinated and the pollen from the catkins blows to reach the female flowers which you would never spot unless you looked carefully – they are tiny individual flowers, visible only as red styles protruding from a green bud-like structure on the same branches as the male flowers.

A female hazel flower - the tiny red styles can be seen protruding from the green bud-like structure on the branch. The styles are each just a few milimetres long so you need to look closely to spot them amongst the catkins!
A female hazel flower – the tiny red styles can be seen protruding from the green bud-like structure on the branch. The styles are each just a few milimetres long so you need to look closely to spot them amongst the catkins!

Hazels typically begin flowering in January and will go on into April, although there were open flowers in December this winter. Once pollinated in the springtime, the female flowers set to work producing the hazelnuts which ripen in the autumn.

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A hazel nut – the eventual result of the pollination of the tiny female flowers with pollen from the male catkins. This photo taken at the end of August before the nuts are yet fully ripe.

Hazel flowers are an important source of pollen for bees, especially those individuals which have overwintered and emerge early when there is little alternative pollen available. Bees collect pollen in medium sized pellets as it is a source of fats and proteins. This is distinct from their need for nectar which is a sugary food source to provide energy and allow production of honey.

A close-up shot of the many male flowers which each make up a hazel catkin. It is these flowers which produce the pollen gathered by bees in the early springtime.
A close-up shot of the many male flowers which each make up a hazel catkin. It is these flowers which produce the pollen gathered by bees in the early springtime.

Hazels are wind pollinated and do not therefore require bees for pollination, although it is noticeable that the female styles are pigmented which may indicate an attractive function. A paper by Pietrowska mentions that the bracts of hazel are adapted for pollen retention. This means that the pollen collects when it leaves the male flowers rather than scattering immediately to the wind – this benefits wind dispersal but also facilitates the collection of pollen by bees. Perhaps the red pigmentation of the yellow flowers is a trick to entice bees  into making the occasional visit to a red female flower, in the hope that nectar may be available, and therefore supplementing the primary wind pollination strategy?

A hazel in the Cotswolds in full flower in January 2015.
A hazel in full flower in January 2015.