Hazel – Corylus avellana

Common name: Hazel

Scientific name: Corylus avellana

Introduction: The Hazel (Corylus avellana) is a deciduous broadleaf tree that is grown across Europe, North Africa and Western Asia.  

Identification

Leaves:  Leaves of a Hazel are round to ovate in shape and are a vibrant green colour before turning yellow in the autumn. They are doubly toothed and soft to touch due to having downy hairs on their underside. They also taper to a point. 

[Leaves of a Hazel tree]

Buds: Their buds are ovoid, blunt and hairy. 

Bark: The bark of a Hazel tree is smooth and grey with the tendency to peel as the tree matures.  

Reproduction

Hazel trees are monoecious; however, their female flowers need to be fertilized by pollen from other hazel trees (the same tree can’t pollinate them). Male hazel catkins that are yellow in colour hang in clusters from mid-February before the leaves begin to form. Their female flowers are small and bud-like with red styles. These get pollinated by the wind and develop into oval–shaped fruits that hang in groups of 1-4. Over time, these fruits develop into nuts with woody shells that are surrounded by leafy brackets – hazelnuts.  

[Male Catkins of a Hazel Tree]

Growth Habit

When left to grow naturally, Hazel trees averagely reach 12m in height and grow to be 80 years old. However, Hazels are commonly coppiced, which can help to extend their lifespan to several hundred years instead.  

Ecological Importance

Hazel trees have substantial ecological importance, helping to provide not only a food source to many animals but, when coppiced, help to provide a sheltered habitat for ground–nesting birds such as Nightingales.  

In terms of a food source, many components of a Hazel tree are favoured by wildlife. For example, their flowers help to provide an early pollen source for bees (despite being harder for them to collect) and their nuts are favoured by Dormice and a range of birds such as Woodpeckers, Nuthatches and Tits.  

Their trunks are also commonly covered in a range of mosses, lichens and liverworts. 

Maintenance

Pruning and Pruning Qualities: Hazels generally require pruning to maintain their appearance and to keep them healthy.  It is also ideal to prune them so that they retain energy for the production of nuts.  

Like most trees, Hazels should also have any dead, diseased, decaying or congested branches pruned out as and when spotted to help prevent the spread of pests and diseases but also to promote better light penetration and air circulation. Suckers should be removed too. 

They respond well to hard pruning such as through coppicing or pollarding which has been known to help encourage vigorous regrowth and the growth of colourful stems. Pruning of this nature should be postponed until a Hazel tree is at least 1-2 years old as hard pruning is not suitable for young hazels. 

Ideally, when carrying out general maintenance, pruning should be carried out between late winter to mid-spring before new leaves begin to appear. Preferably, this time is also when resources are focussed on the roots of a Hazel which in turn helps with regrowth. Pruning outside of this time will have an adverse effect 

If you are ever in doubt about what pruning your tree may require then you should always contact your local tree surgeon who can answer all your questions. You can find your local tree surgeon here.  

Growth Rate after Pruning: After hard pruning through coppicing or pollarding, Hazels can experience vigorous regrowth. This also helps to extend their lifespan from an average of 80 years to several hundred.