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.
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.
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.
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.
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?
Willows (Salix genus) are one of the earliest flowering tree species in the UK and are a fantastic nectar source for early pollinators such as bumblebees and butterflies. These trees are dioecious which means that there are separate male and female trees which can be distinguished by their flowers. Another more commonly known example of a dioecious tree would be the holly – only the female trees bear the red berries. One of the traditional names for willow flowers was ‘vegetable goslings’ which seems a perfect description to me!
The flowers are quite unusual when compared with a simple flower such as a buttercup which follows the classic textbook diagram. Willow flowers are catkins – these are spikes of numerous tiny flowers rather than each catkin representing a single flower. Each of the yellow-tipped spikes in the male flower is one of the stamens and there are generally two or more of these to each individual flower within the catkin – the number varies with species. The same is true, although less easily illustrated, for the female flowers which have two or more stigmas per flower.
The male and female flowers appear at the same time in order that the pollen from the male flowers is able to fertilise the female flowers. The flowers are quite different from one another in appearance and, side by side, it would be easy to assume that a male and a female willow tree were two different species.
The willow flowers are an excellent source of nectar for early pollinating species, such as queen bumblebees which have emerged from hibernation and are establishing nests, or the early Nymphalidae butterflies which hibernate through the winter.