Common hazel (Corylus avellana): Looking at the heritage of two native trees in the UK

NOT so long ago, a high-profile TV presenter and acclaimed botanist sparked controversy by claiming racism is endemic in UK gardening (and by implication horticulture and forestry) with “fetishisation” and “wild misuse” of words like “native” and “heritage”. 
Normally I wouldn’t take much notice of such spats, but this one impacts directly on what I do. ‘Heritage’ and ‘native’ are two highly useful words, so I will afford them as much use as possible, just in case they are banned. 

I love woodland, but hedgerows even more so. I think it has something to do with illumination and how the well-designed and managed hedgerow bathed in full sunlight can support a much wider range of herbaceous plants, insects and bird life, compared with classical woodland. So the two native species I have chosen for their heritage status are common hazel (Corylus avellana) and hedgerow hawthorn (Crataegus monogyna).

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No others are more steeped in the history and culture of the British Isles. Both are true natives, exploited over many centuries for fuel, building material and fencing, while remaining of limited interest to the timber merchant or woodworker due to a sparseness of wood with which to work. 

These stubborn species thrive in the widest range of environments, often continuously cut to satisfy basic essentials of rural life. As such, they rarely achieve full size and natural shape as mature trees, but continue to hold special places in age-old ceremonies, cultures and customs throughout the land. 

Neither features on the list of native trees considered susceptible to climate change in the British Isles (no surprise there, since the natural range of hazel and hawthorn includes North Africa and Western Asia). Both are early spring risers, but hazel, with its iconic male catkins (lovingly called ‘lambs’ tails’), is first and so deserves to be explored first.

COMMON HAZEL (CORYLUS AVELLANA)

Native common hazel has been bound up in superstition since Celtic times. However, the species was rarely allowed to attain full size because it was more valuable when grown and cut as coppice, an age-old practice greatly expanded in Tudor times.

Sheep and wool were mainstays of Tudor England’s economy but grazing sheep closely cropped the land, offering hazel and other tree species precious little chance to establish.

This led to the practice of fencing in and establishing hazel coppice on a portion of the very best land in every village, with individual coupes (compartments) cut on a traditional 7–8-year rotation, providing brushwood bundled into faggots for firing the bread oven, stakes, thatching spars and wattles for wattle-and-daub house building.

Most importantly it made the woven hurdles (fences) used to enclose grazing animals.

uch of England’s remaining hazel coppice is managed by volunteers from local community groups. Paul Clark, a founder member of Friends of Bunkers Park at Hemel Hempstead in Hertfordshire, who has planted, cut and processed the hazel coppice at Bunkers Park over a 20-year period.

Every one of these examples clearly shows how hazel, more than any other native tree, provided the essential needs of everyday living. 

Short-rotation hazel coppice was widely practised for centuries, and when you find an ancient hedgerow in southern England, rich in hazel but with little or no hawthorn, you are almost certainly standing where once was coppiced hazel. In spite of sustained cutting over many centuries, hazel has always grown back to provide one of the most congenial habitats for small mammals, birds, butterflies and flowers: 

The poplars are felled, farewell to the shade
And the whispering sound of the cool colonnade
The blackbird has fled to another retreat 
Where the hazels afford him a screen from the heat
from ‘The Poplar-field’ by William Cowper (1731–1800), English poet and hymn writer.

Hazel coppice is now a shadow of its former glory, but the word ‘copse’ lives on to describe many of today’s small woodlands, some still carrying the name of the man who did the cutting centuries ago.

The tree was closely associated with the earliest of our ancestors, so it is not surprising that hazel has a central and positive role in Celtic folklore. Known as the tree of knowledge with white magic properties, it was used to alleviate fear and suffering throughout the British Isles. Aches and pains in the ancient Irish, whether caused by the damp climatic conditions or ‘elfin malevolence’, were warded off by carrying a hazelnut on the person. Double hazelnuts were said to cure toothache in Devon and deter witches in Scotland. Hazel along with hawthorn and mountain ash (rowan) in Scotland were the trio of true native trees having white magic properties and used on May Day to fight forces of evil that were thought to inhabit native forests and woodlands. 

And we danced around the may-pole and in the hazel copse,
Till Charles’s Wain came out above the tall white chimney-pots
from ‘New Year’s Eve’ by Alfred, Lord Tennyson (1809-1892)

The end game for hazel came with widespread adoption of wire fencing to enclose sheep at the expense of hurdles woven from hazel and has been associated with the post-World War II period. At the end of WWII there were over 160,000 acres of hazel coppice and scrub throughout the country, with only that on some Scottish hillsides (e.g. Argyll) and the Lake District regarded as truly wild. The majority, in the south and midlands of England, had its roots in the very beginnings of 15th-century forestry.

Hazel coppice seen here beyond its normal 7–8 year cycle, but still surrounded with bluebells at the end of April.

Only a tiny fraction of the 160,000 acres remains today, but the precipitous falling away of worked hazel coppice actually started at the turn of the 20th century, not halfway through it. Be that as it may, common hazel is now just as likely to be found as a shrub in hedgerows as residual, understorey growth in woodland.

LAMBS’ TAILS WAG IN THE WIND

The flowering stage in trees goes largely unnoticed, but hazel is an exception. On bright winter days, the sausage-shaped male flowers, formed in the dying days of the previous summer, loosen and lengthen to become pendulous catkins called ‘lambs’ tails’. 

In the full light of day they assume a delicate yellow but appear amber in the late afternoon sun of early spring. The catkins or lambs’ tails traditionally started to swing in the breezy days of early and middle March, flying like flags and throwing yellow dusty pollen to the wind of the vernal equinox.  This was the traditional timing which I remember from six decades ago, supported by the comments of botanists like G.S. Boulger (Familiar Trees, circa 1900) who said: “Each catkin consists of a number of bract-like scales, each of which bears eight anthers on its inner surface, so that a cloud of fine-grained yellow pollen is shaken from them by the March gales.”

However, hazel appears to have been waking up increasingly early from winter dormancy, especially during relatively mild winters (like 2021/2022) when there were fully lengthened and loosened lambs’ tails during those sunny days in the first week of the new year. The downside is premature death from hard frosts and snow in February and March like the now infamous Beast from the East in 2018.

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The female inflorescence is inconspicuous as a small bud at the branch tip, except for the bright-crimson stigmas protruding through the apex of the clustered flowers. These are pollinated and fertilised via the wind, subsequently fed by the large leaves and developing into hazelnuts, the only edible nut kernel produced by a truly wild and native British tree.

THE LEAVES – A POWERHOUSE OF PHOTOSYNTHESIS

Young expanding leaves on new spring growth of coppice stools cut during the previous winter offer the observer a flash of orange and red, but thereafter are uniformly green throughout summer and turn completely yellow in autumn. 

Despite the small size and understorey position of common hazel stools, they are a powerhouse of photosynthesis. By the end of the first growing season after coppicing, regrowth will regularly exceed one metre in height. Recent measurements taken in fertile woodland in South Hertfordshire showed hazel coppice stools of 30 cm diameter producing 12 new stems (rods) up to 150 cm in height and bearing about 25 leaves each by the end of the growing season during September. 

By October, hedgerow hazel will have been stripped of its hazel harvest by grey squirrels. This lone nut was a rare one which got away.

Hazel leaves are essentially circular in shape and these were large leaves. For the 25 leaves up the hazel stem, the length of the lamina from its insertion on the petiole (leaf stalk) to the leaf tip averaged out at 12.4 cm to give an approximate average leaf area of 120 cm². Multiply this by 25 leaves per stem and 12 stems per coppice stool and you get a leaf area of 3.6 m² per coppice stool in the first season after cutting; truly amazing when you consider that the stems are only around 1.5 m high.

HAZELNUTS IN DEMAND FROM MAN AND BEAST

Hazelnuts are tasty and nutritious but human nut gatherers need to be quick off the mark to beat grey squirrels. Other woodland animals take the nuts for food, but the one most closely associated with hazelnuts is the hazel dormouse (Muscardinus avellanarius).

This nocturnal rodent is almost impossible to spot, but such is the closeness of its association with Corylus avellana that evidence of its whereabouts is traditionally established by close inspection of fallen hazelnuts for tell-tale signs of a meticulous opening. Dormice open the nuts by making a neat round hole on one side and leave signature tooth marks around the margin of the hole. 

Dormouse damage to hazelnuts is so specific that it has been used by the UK’s National Dormouse Survey to identify and monitor dormouse populations under the title ‘The Great Nut Hunt’. The survey, which has operated with support of leading conservation bodies including Natural England, the Woodland Trust and the Forestry Commission, identifies woodland trends, specifically related to hazel coppice, and which may be responsible for the well-documented decline of the hazel dormouse. 

Gone with the demise of hazel coppice is the ideal woodland environment for dormice, comprising sprawling branches and therefor safe pathways above the ground and a wide variety of different shrubs for food, harbourage and shelter and without too much shade.

As nature intended – native seven-spot ladybird (Coccinella septempunctata) on native common hazel.

Conservation bodies are encouraging landowners to bring back this traditional form of hazel management, but stress the areas should not be too large and must offer sufficiently long periods between one coppice cut and the next (15–20 years and at least twice the traditional rotation), to permit hazel trees to grow and produce nuts. Hazel is usually propagated by nuts, which should be kept cool and moist from harvest in the autumn until planting in spring. 

Dormice are not the only creatures to leave their ‘calling card’ on the hazelnut shell. If you look at hazelnuts in autumn you may see a minute round hole bored in the shell that means that hazelnut weevils, Balaninus (Curculio) nucum, have been at work inside.

During the early part of summer the adult female weevil targets hazel trees and the young, soft green nuts. Using its snout the weevil bores deep inside and lays a single egg into the nut. From this hatches a fat white larva (grub) which feeds on the kernel until the nut falls in the autumn. Now mature, the larva exits through the shell and pupates in the soil until spring when it emerges as an adult weevil.

WOOD, WANDS AND WATER DIVING

You cannot leave hazel without mentioning its long-standing relationship with water and the tree’s preference for a moist, fertile soil. The tree will not tolerate very acid and/or waterlogged soil conditions, although hazel rods or wands were widely used as water diviners. Water was very much in the mind of the iconic Irish poet William Butler Yeats (1865–1939) when he wrote ‘The Song of Wandering Aengus’:

I went out to the hazel wood,
Because a fire was in my head,
And cut and peeled a hazel wand,
And hooked a berry to a thread;
And when white moths were on the wing,
And moth-like stars were flickering out,
I dropped the berry in a stream
And caught a little silver trout.

Though rarely talked about now, the whitish-red hazel wood, close and even in grain, soft, highly elastic and easily split, was used in turnery, while well-veined veneers were taken from the larger roots. Under the light microscope, hazel wood exhibits some very broad pith-rays, radial lines of small xylem vessels, and almost circular annual rings. 

For such an undistinguished looking tree, its wood is widely travelled. Huge numbers of hazel hoops cut to a range of sizes were traditionally shipped straight in bundles to wine-producing countries for training grapevines and to Jamaica in the West Indies to bind cane sugar barrels.

There are incentives to plant Corylus avellana as an ornamental and amenity tree using bred varieties like C. avellana ‘Aurea’ with soft yellow leaves and C. avellana ‘Contorta’ (corkscrew hazel) with its peculiar twisted branches.