While traditionally mistaken for beech, the hornbeam is a tree with its own distinct history, features, and importance.
THE name hornbeam encapsulates the features of a gritty and resilient native tree (Carpinus betulus) which is bedded in the birch family (Betulaceae) with silver birch, hazel and alder. This relatively slow-growing tree develops a fluted bole of wood as hard as horn and with a calorific value rivalling that of Welsh anthracite. Hornbeam will coppice and pollard with the best of the rest to yield a high-energy biomass, which burns like a dream. Despite the tree’s high versatility, hornbeam is less well known and appreciated than many other native trees, for two key reasons.
The first is the tree’s relatively late appearance in the British Isles. Like common beech (Fagus sylvatica), hornbeam was one of the last broadleaf species to cross over from Europe after the last ice age. Its natural spread northwards and westwards was inhibited by other well-established trees essentially confined to southern England, but like beech, hornbeam was planted much further afield. However, hornbeam’s original natural distribution remains essentially intact. Semi-natural broadleaf woodland in south-eastern English counties like Essex, Hertfordshire and the ‘old’ county of Middlesex remains rich in hornbeam coppice and pollards under oak standards.
Herein lies the second reason for hornbeam’s relative obscurity. Its traditional use as woodfuel means hornbeam has persisted as coppice and understorey to oak standards and, as such, is not at all prominent in the woodland or in the eyes of the general public. Indeed, hornbeam remains one of the least well-known native trees, even in those English counties just north of the River Thames where the species frequently dominates.
That said, uncut hornbeam will grow, albeit slowly, into a large standard tree, but woodlands where this has historically been allowed to happen are few and far between.
Hornbeam goes under other common names like ‘ironwood’ (widely used in North America) due to the extreme hardness of its wood, and ‘Lanthorn’ because the wood burns with a bright, yellow flame. Hornbeam trees do not sucker, but can regenerate and propagate strongly via the seed. Hornbeam is quite tolerant of poor soils, one of the reasons Carpinus betulus makes good hedgerow material.
Hard and hardy hornbeam trees have the grit required for stability in the face of changing environmental conditions, whether from pollution or the not-unrelated dynamics of climate. Hornbeam has a strong preference for shady woodland environments, while offering a sound choice for amenity and landscape planting – especially custom-bred biotypes like ‘Pyramidalis’ or ‘Fastigiata’.
The handsome hornbeam tree
Hornbeam trees growing on poor, dry soils will not attain their full potential, but sink the roots into good-quality lowland clay or a rich loam and a 20-metre-tall tree canopy supported by three-metre-girth bole will loom.
The heavily fluted bole of a hornbeam standard, covered in smooth, pale grey bark, will usually grow straight up in woodland, but will frequently be angled when growing outside. The trunk divides into many limbs that sweep up to form a densely branched and symmetrically shaped crown. Winter buds are pale brown in colour, borne alternately along the slender, delicate twig, closely pressed against it to resemble a crouching mouse.
Male and female catkins on this monecious species are fully active by early April, which is just before the leaves unfurl. Both male and female flowers are set in positions towards the tips of the twigs. Male catkins loosen into a pendulous chain of overlapping yellow-green bracts and shed their pollen from a cluster of orange anthers tucked under each bract.
Female catkins comprise a loose cluster of leafy green bracts with tips curled upwards. Beneath each bract is a pair of smaller bracteoles to protect the red-coloured and sticky stigmas which intercept pollen grains from the air.
New leaves slowly emerge from the sheath of pinkish-tinged bud scales in a fan-shaped mode. When fully unfolded, the leaves are 3–10 cm long and oval in shape, with a serrated margin and an upper surface characteristically creased along the lines of the leaf venation.
Pollination and fertilisation produces a pair of nutlets eventually becoming 3–6 mm long. Each one is formed in a shallow cup and each bracteole enlarges into a three-lobed wing with the central lobe the longest. The asymmetry of this seed-wing plays a pivotal part in fruit and seed dispersal starting in September, by initially acting as a sail to catch the wind and steer the fruit, but subsequently causing it to gyrate (spin) to carry the enclosed seeds a good distance from the tree.
Autumnal colour change is variable depending on where the tree is growing. By mid-October woodland hornbeam trees will bear yellow leaves, turning gold, then brown, falling around the same time beech leaves are at their very best.
When growing in open-aspect situations like hedgerows, hornbeam canopies will often suffer an early autumn colour change in August, with the leaves drying out quickly and browning by early September without turning yellow. Leaves on young hornbeam trees and shrubs in amenity hedges may remain attached to the twigs in a shrivelled, brown condition throughout winter, as frequently happens with beech and oak.
The ribbed nutlets which enclose the single seed provide vital food supplies for woodland birds and mammals, especially hawfinches, whose English distribution traditionally matched that of the hornbeam. Squirrels are not averse to hornbeam nutlets, climbing the trees to eat these fruits or retrieving fallen nutlets from the forest floor. Those which survive wild animal feeding lie dormant for up to 18 months before germinating.
Hornbeam at home under oak
Hornbeam and English oak have been bedfellows for a long time, but not always. Pollen records show hornbeam as a relatively late arrival into southern England, after crossing the land bridge which connected with Europe, while oak, which arrived 2,500 years earlier, was already widespread across Britain. Despite a traditional status as an understorey woodland tree, hornbeam can be found as a full-sized, standard tree of the hedgerow, but is more likely to be found as a component shrub of the actual fabric of the hedge. Hornbeam is highly underrated as an amenity and landscape tree or as the sole component of hedges in these sectors.
Confusion with beech
Naturalist Edward Step said hornbeam was frequently mistaken for beech due to some general superficial similarities. In the relative darkness of woodland understoreys I have frequently confused the two as young trees, although with closer scrutiny of the bole, leaves and flowers on older and bigger trees it is easy to separate the species. Mixed hornbeam and beech hedges are not infrequent in the amenity and landscape sectors, although whether that is by accident or design is unclear.
Superficial similarity between beech and hornbeam has been put to good use in avenue-tree planting. The iconic Beech Avenue, which flanks the B3082 between Wimborne Minster and Blandford on the Kingston Lacy Estate in Dorset, was planted in 1835, with 731 beech trees planted either side of the then-new road, 365 one side and 366 the other, to represent one for each day of standard and leap years.
In 2010, the 175-year-old trees were deteriorating fast from a combination of traffic pollution and a disease caused by the fungus Kretzschmaria [Ustulina] deusta, the former probably helping the latter by physiologically weakening the trees. At the time, the National Trust said all beech trees requiring felling and removal would be replaced with hornbeam trees, on the grounds that hornbeam provides similar autumnal interest and, as such, blends in well with the existing beech trees. The National Trust also said hornbeam would be far better placed to cope with changing soil and atmospheric conditions along what was increasingly developing into a high-traffic main thoroughfare.
Be that as it may, there is little room to confuse hornbeam and beech for the experienced eye. Winter buds of hornbeam are much shorter and fatter than the exceptionally long and pointed ones of beech. What’s more, they hug the twig, whereas beech buds are set at an angle to the stem. Tree size, shape and structure are sufficiently distinct, except in ancient woodlands where both were traditionally pollarded.
The bark of both is light grey and smooth, but that is where bole similarity ends. The bole of the hornbeam is extremely convoluted and flared, to a degree that exceeds all other British native broadleaf trees – nothing like the typical woodland beech tree with a straight, columnar bole.
The generally accepted view is the name hornbeam describes the ‘hornlike’ character of the tree’s wood, although others say it harks back to the days when a pair of bullocks was yoked to the plough using a yoke made of hornbeam and, being attached to the animals’ horns, it was logically called the ‘horn-beam’. The third and least likely option is hornbeam being derived from Ornus, the Manna-ash, and a tree which hornbeam was often confused with by early botanists. However, most people preferred the original offering and in doing so were clearly on side with ‘old’ John Gerarde who said in his Herball (1635): “In time it [hornbeam] waxeth so hard that the toughnesse and hardnesse of it may be rather compared to horn than unto wood, and therefore it was called hornbeam or hard-beam”.
Hornbeam has the distinction of growing the hardest wood of any tree in Europe. Hornbeam is heavy, fine-grained, and creamy yellow in colour but has never found much application as timber because the heavily fluted trunks caused undue wastage when trying to saw out the planks.
Cabinet makers and joiners never used much hornbeam because it was too hard, blunting tools quickly and wasting time in their re-sharpening. However, hornbeam did find a place in making instruments and items for which hardness was a top priority, including the hammers of piano-keys, skittles and skittle balls, golf club heads, shoe lasts and plane stocks. Other applications and uses for hornbeam wood were in parquet flooring, carving boards and tool handles. Hornbeam was the traditional engineer’s wood for heavy-duty purposes, used for making cogs, pulleys and wooden screws before iron came into common use. Hornbeam was specifically used for ‘bushes’ on which wooden rollers turn, especially those which carried the saw-bench in the traditional woodland sawmill. Gear pegs for windmills were invariably made from hornbeam.
Hornbeam wood burns well and prior to coal was England’s major source of energy.
Hornbeam woods to the north and north-east of London, such as Epping Forest in Essex and the Enfield Chase, which once straddled north-east Middlesex, were heavily coppiced and pollarded. The wood was used to heat homes and converted into charcoal to fire the furnaces of England’s capital city.
Hornbeam charcoal burned hot enough to smelt iron.
Hornbeam in the shade
Hornbeam as a native tree continues to play an important role in the wider environment, with specific historical and traditional roles in south-east England’s agricultural, industrial and community development over the millennia.
That said, you can’t help but conclude that as an understorey tree hornbeam has always been in the shade of others, especially English oak, with which it is commonly found, and also beech, which for some apparently peculiar reasons, hornbeam is often confused.
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