It may perhaps be doubted whether monstrosities, or such sudden and great deviations of structure as we occasionally see in our domestic productions, more especially with plants, are ever permanently propagated in a state of nature.

Charles Darwin, On the Origin of Species

Darwin and most of his peers had no conception of what we now know as genetics, the biological processes that determine how traits get inherited and expressed in progeny, and how mutations occur. It wasn’t until the time of Hugo DeVries (1848–1935), who coined the word “gene” before learning of Gregor Mendel’s pioneering work on heredity, that the term “mutation” came to be applied toward biological entities, and the phenomenon it names seen as a possible driver of evolutionary change. Darwin and his peers did recognize sudden changes to a species’ appearance, which they called “spontaneous variations,” “sports,” and “monstrosities.” There were vigorous debates over the rate of biological change to species, with Darwin arguing for gradual change, stating, Natura non facit saltum: “Nature does not jump.” De Vries and others, however, advocated that sudden shifts in species could occur. The German geneticist Richard Goldschmidt took up this argument in his book, The Material Basis of Evolution (1940), asserting that “the change from species to species is not a change involving more and more additional atomistic changes, but a complete change of the primary pattern or reaction system into a new one.” He came up with the colorful term “hopeful monsters” to describe these sudden shifts in the genome.

As a walk through most any garden center will suggest, the field of horticulture is a parade of hybrids and mutations: larger flowers, abnormal colors, muti-colored leaves, atypical habits, and on and on. As a member of the propagation staff at the Arnold’s Dana Greenhouses long ago, I found it impossible not to be attuned to mutations. Not only did we propagate atypical forms from the collection as grafts or cuttings, but we were always on the lookout for an aberration in a flat of seedlings to isolate and grow on. The Arnold rightly shifted away from horticultural selections to wild-collected material; but commercial, corporate horticulture remains largely a catwalk sashay of this year’s “hopeful monsters.”

In doing fieldwork for the Arnold, I would occasionally spot mutations in nature—a variegated branch on a Chamaecyparis thyoides at Ponkapog Pond in Milton, Massachusetts; witches brooms on the occasional conifer. As Darwin suggests, however, these generally are rare, and need a keen eye to spot. I have never been in a forest where a mutation presents itself so dramatically and with such frequency as the beech forests in the southernmost län (county) of Skåne in Sweden. There, the tortured or parasol beech, Fagus sylvatica ‘Tortuosa’, stuns the eye and challenges the mind.

The European Beech

The species Fagus sylvatica, the European beech, has a very wide range in Europe, from the Cantabrian Mountains of Spain to the Carpathians and Balkans of eastern Europe, and from Sicily north to southern Sweden and Norway. The few Norwegian stands have been shown to be genetically connected to Danish populations, and are now thought to have been transported by human agency long ago, possibly as pannage for pigs on Viking ships.

Under the right conditions, the European beech can attain massive size, as much as fifty meters tall with girths up to eight meters. The altitudinal range of the species can be as high as two thousand meters in Spain and Sicily, to low coastal altitudes in the northern parts of the range.

There are about sixty named horticultural selections or cultivars of European beech: fastigiate, weeping, red leafed, tricolor leafed, fern leafed and on and on. But none, to me, match the mysterious tortured beech, Fagus sylvatica ‘Tortuosa’.

I first came across this tree in 1977 while cross country skiing through the Arnold Arboretum on a snowy winter day. I slid downslope into the magnificent beech collection and was astounded at the site of the tortured beech. In 1996, I wrote about this astonishing sight in the June issue of Natural History Magazine:

Standing only twenty feet high after one hundred years, this tree surely has battled for every inch, rising from a splay of roots, its trunk is a curving, silvery gray column, encrusted with knobs, warts, and carbuncles. The lower branches have grown out, contorting backward and grafting themselves into the trunk to form odd cup handles, or “horse collars.” Clusters of main branches writhe upward, then branchlets zigzag down to the ground. The crown forms a dome of serpentine branches, a parasol fit to shade a Mad Hatter’s tea party. Where the bark has fallen off, the contorted growth pattern of the wood is exposed; it looks more like tightly folded igneous rock than wood. This tree is botanical chaos, Quasimodo in wood.

A picturesque dusting of snow only highlighted the crazed architecture. It instantly became, and remains, my favorite tree in the collection. But what was the origin story of this fantastic beast?

The earliest written report of these curious trees, from Denmark, dates from the 1840s. The French botanist Pierre Denis Pépin was the first to apply the ‘Tortuosa’ epithet in 1861, beginning a long line of French botanists who wrote about the twisted trees of the Verzy forest in northeast France, perhaps the most famous stand. Élie Abel Carrière in 1864 described the trees as “a riddle to the scholars, a challenge to all plant theories.” He offered up my favorite description of the otherworldly mutants: “imagine a number of snakes in a bag, and then imagine hitting the bag with a stick; the reptiles would contort themselves in such a way that all the individual forms would join in a hideous and bizarre group. Such is more or less the general form that the monster beech trees of Verzy exhibit at the point where they branch out.”

Large clusters of the tortured beech have been recorded in forests in six countries. Within northeast France, Parent notes over eight hundred specimens of “Faux de Verzy” in an area 100 by 250 kilometers, concentrated mainly around Verzy; In the Sjaelland (Zealand) region of Denmark, “Vrange bøge” (twisted beech) also are found; the Weserbergland in Lower Saxony (North Central Germany) hosts some four hundred wild trees of “Süntel-Buchen”; and in Sweden, near Dalby in Skåne, about 1100 trees of “Vresbok” have been recently inventoried. Additional smaller groups have been documented from Mt. Pollino in Italy (“Alberi serpente”), and 40 specimens of “Vilina bukva” at Batočići in Bosnia and Herzegovina.

Since that snowy day in 1977, the tortured beech had been on the wish-list of trees I planned to see in their wild state. My chance came about when I undertook a plant-collecting trip to Norway and Sweden in 1993 for the purpose of collecting wild English yew (Taxus baccata) for anti-cancer research. I contacted an old and respected friend, Karl Flinck, a former business executive and self-taught dendrologist, who nurtured his own private arboretum in southern Sweden. I wrote of my intent to visit Scandinavia and, if time allowed, to visit the grove of beech at Verzy, France. He wrote back with an invitation, thrilling me with the news that a grove of monster beeches was but an hour’s drive south of him. With my four-year-old son in tow, we visited Karl and then the trees near Dalby, photographing about a dozen.

The path wound under the old, contorted canopies, which stood like so many frozen snakes writhing above our heads.

Little could I have known that thirty years later, my son would be a postdoc at Lund University in Sweden and, joined by my wife and his mother, Ida Hay, we would make the trip again, visiting Skåne twice between 2022 and 2023. When Charlie and I had visited Karl Flinck long ago, the four-year-old Charlie absolutely charmed our host when he said, “you know, I think Karl is a man of nature.” It was nice to see that my son, a specialist in pollination ecology, had grown to be the same. I had hoped that my Charlie’s new son Cyrus would join to make the first foray a three-generation affair, but he was not quite forest-ready. As a one-year-old, my grandson did make the cut on our most recent visit to the forest, however, foreshadowing another generation keeping company with the natural world (when not fast asleep).

A Walk with Trolls

After two bus rides from Malmö, we disembarked at the village of Torna Hällestad and walked down Trollskogsvägen (Troll Road) toward the nature preserves that held the trees. Following a trail that paralleled the railroad tracks before cutting across some open fields, we passed through a livestock fence and crossed into the Prästaskogen nature reserve, then up onto a glacial moraine, getting into forest. Our initial tree with contorted branches had a normal trunk and thus was, as we would soon find, an intermediate form. We continued along the ridge path and soon were awed by a succession of tortured beeches. Each was different, varying degrees and styles of contortedness and different ages. Some were sixty feet tall, bent branches atop a fairly straight trunk, while others grew contorted from the ground up. You could pick out mutated saplings from normal young beeches, as the mutation expresses at an early age. Individual tortured beeches punctuated the slope of normal trees, but also appeared in picturesque clusters. The path wound under the old, contorted canopies, which stood like so many frozen snakes writhing above our heads. One extreme tree stretched a remarkably massive and twisted branch across the path, a writhing, wooden anaconda you had to duck under to pass. After a lifetime of collecting “normal” trees in the forests of the world, I had never seen anything like it. The presence of non-mutated beeches all around only increased the sense of right and wrong.

On the path in the Prästaskogen nature preserve outside Torna Hällestad.

We cut off the path toward the light of an open field, at the edge of which stood a tortured beech dense with three-angled, spiny nuts—so tempting to collect, though I had no permits, and had to pass. The full sun exposure seemed to bring greater fruit set and tighter branching. Turning downslope, we crossed a shrubby meadow, seeing old friends like Euonymus alatus, Symphoricarpos albus (non-native), and Calluna vulgaris. We climbed another livestock fence and were immediately in another grove, called by locals Trollskogen, the Enchanted Forest. This proved to be a denser concentration of trees spread over several acres with some spectacular groupings of twisting, convoluted trunks and branches. Local people once believed these trees to be trolls, who were either cursed into their current form or could transform back into their original bodies at night. Dozens of the wooden monstrosities presented themselves, each unique in form and genetics. It struck me as improbable that this perfect set for movies with hobbits, witches, vampires, and trolls had never found its way onto the screen.

Alongside the road, as if planted together, a cluster of four trunks stood twisted about each other—sculptural, mystic, almost beyond description, another clan of dancing arboreal dragons. We continued up the Trollskogsvägen to Gryteskogen, another dense cluster of Fagus sylvatica ‘Tortuosa’, where we found one specimen that showed a “horse collar” growth: a branch that had extended out, contorted back to the trunk, and grafted itself on, forming a crazed teacup handle that could catch a horse’s head. It did catch a few botanists that day. After passing through a mossy fieldstone wall that reminded us of New England, we came upon a final large, magnificent specimen.

All told, we probably saw a hundred contorted beeches in a few hours, and by no means saw them all. A great day in the forest was only made better at a bus stop cafe, with its pastries and dark-roast coffee. Between sips, it occurred to me how many versions of the mutation we saw, all different and unique. I had propagated many plants of the Arnold’s tree via grafting (a thirty-year-old specimen grows in the backyard of my Boston house), but I now realized what a small fraction of the total story the Arnold’s two trees represented. It is like a one-inch square snipped from a vast canvas by Monet.

Cause and Effect

Prior to botanists trying to explain the trees, local peoples would attribute religious, mystical, or mythological reasons for the twisting growth; my favorite name for a tree, in German, which translates to “Devil’s Pulpit,” bears this out. French botanists theorizing about cause prior to the advent of genetic theory suggested that the iron soils of the region of Verzy caused the deformity. In 1906, Henry James Elwes and Augustine Henry discussed the tortured beech in their classic tome, The Trees of Great Britain and Ireland. Their section on the tree sounds a decidedly genetic note: “fruits of this form have been sown in the garden of the Forest School of Nancy, and have reproduced the twisted form in the proportion of three-fifths; the other two-fifths of the fruit produced form like the common beech and intermediate varieties.” Thus Elwes and Henry observe the heritability of the mutation, further noting that only three-fifths of the offspring exhibit the tortuous form—as we understand now, evidence of genetic mutation. Later researchers have found the mutation in 25 to 100 percent of seed sown from ‘Tortuosa’.

Distribution of known major wild populations of Fagus sylvatica ‘Tortuosa’ in Europe.

Historically, then, the form of tortured beeches has been chalked up to soil composition and heritability. But my favorite theory of environmental causation involves extraterrestrial forces. As Anthony Huxley observes in his book Plant and Planet (1974), “it is known that artificial radiation will produce mutations…

One of the most remarkable examples of this is the tortuous beech of Europe. In these trees the branches writhe like serpents, often rejoining the trunk or other branches. All are about the same age; and they exist in Denmark, Germany, northern France, and Brittany, mainly in small numbers within an assemblage of normal trees. The remarkable thing is the localities are in a straight line, and one implication is that a radioactive meteorite passing over these places a century ago affected young trees immediately below it.

While I love the comic book premise, and the stands in northern Europe are in a roughly straight line, Huxley conveniently omitted (or didn’t know about) those stands in Italy and eastern Europe that aren’t on his meteoric line. But could the cause have another vector—a genetic chromosomal mutation passed along through pollen and seed, or perhaps a virus, which can also pass through seed?

As the monster beech’s branches grow, the signals to produce the correct mix of hormones seems to vary, switching on and off, resulting in a kind of arboreal schizophrenia.

Trees in the Trollskogen or Enchanted Forest tower overhead.
Younger specimens show how early the mutation expresses itself.
“dozens of the wooden monstrosities presented themselves” (bottom right), “each unique in form and genetics.”

Trees with mutated or abnormal habits differ chiefly in a lack of leader formation (forming prostrate or weeping trees), reduced length between buds (dwarfism), or having side branches that are at a reduced angle to the vertical trunk (columnar). The side branches of non-tortured beeches grow from the trunk within a well-defined angular range; reaching upward at first, these branches may bend into downward growth as they lengthen and put on weight. In ‘Tortuosa’, the side branches do not show any recognizable pattern of growth, but operate under a different set of controls. When I first wrote about the tortured beech in the ’90s, we knew much about the factors that could induce such aberrant growth through these hormones and other chemical growth regulators: Indole acetic acid (IAA), a simple hormone with far-reaching effects, stimulating cell division and differentiation and shoot elongation, originating in the stem tip and leaves, and moving downward through the stem; gibberellic acid, which promotes cell elongation; cytokinins, which also stimulate cell division; and ethylene. These and other compounds combine to produce a range of effects on growth and the formation of wood in the branches of a tree. In most trees, these effects are generally well-regulated. But as the monster beech’s branches grow, the signals to produce the correct mix of hormones seems to vary, switching on and off, resulting in a kind of arboreal schizophrenia. That this outcome has a genetic basis is evidenced by the prevalence of twisted growth even in seedlings, suggesting that these aberrant signals are hereditary. Disease, too, can affect hormone levels; IAA in particular can show increases, and symptoms such as epinasty (downward curving stems) and changed growth rate and form can result. Both bacterial and viral pathogens can skew hormonal balance, the effects of which can be carried along into seed and expressed in the resulting seedlings.


“Genetic bottleneck” is a term for an environmental effect or human act that results in reduction of genetic diversity in a population, leaving the recovered community highly reduced in diversity. It could be said that the Arnold Arboretum has had more bottlenecks than a recycling center, and Fagus sylvatica ‘Tortuosa’ is a perfect example. The record of introduction of this taxon into our country is a little fuzzy. Early accounts of Fagus sylvatica in the United States include Andrew Jackson Downing’s book, A Treatise on the Theory and Practice of Landscape Gardening, Adapted to North America (1841). Though he discusses European beech and various selections such as the red leafed form and weeping form, he makes no mention of the monster beech. The Arnold Arboretum’s database shows it importing the tree three times from Kew Gardens in the UK between 1885 to 1888, and once from Simon-Louis Freres Nursery of Metz, France in 1888. The database has the Kew trees coming from Verzy, and two of these original four introductions survive, both from Kew (it is unclear if all three shipments from Kew were from a single source plant). From the Arnold’s introduction, other botanic gardens and nurseries would obtain scion wood and over many generations the tortured beech became established in American horticulture. I could find no records of importation other than the Arnold’s. While thousands of wild plants of this form exist in European forests and, I would suspect, as multiple clones in European gardens, those plants in the US may represent one to four clones from France. It would be a fascinating genetic study to compare specimens of the Fagus sylvatica ‘Tortuosa’ growing in US and European gardens to determine just how narrow the bottleneck is.

A recent theory, advanced by French researcher Jacques Bierne in 2017, suggests a transposon was involved within the beech itself. Transposons (jumping genes) are sections of chromosomes that can move from one location on the genome to another. Noting that some tortured beeches in France would throw off sections of new growth with normal branching architecture, a retromutation, Bierne concluded the ability of the contorted branch mutation/architecture to undergo a reversion again, back to normal growth, validated his theory that “the mutation of the gene involved is attributable to the mobility of a transposon.” I have seen dwarf Alberta spruces and other dwarf conifer mutations do a similar shift to normal growth, so perhaps this theory applies to other taxa as well.

Perhaps the most confounding mystery within the tortured beech saga is that I saw a few specimens of tortured oak next to the beeches in Skåne; such oaks are also known from Verzy. No hybrids between Fagus and Quercus have been seen, though they are in the same family and frequently are found together in the wild. Neither are there cultivated selections of contorted oak, though “curly oaks” are noted in some places in Europe. This might point to a common external causality—perhaps an organism that can both infect and mutate both genera. Or—though a long shot—might this be an example of horizontal transposon transfer (HTT), in which a transposon (the section of genetic material containing the mutation) is transferred via microorganism, pollen, or root-to-root contact, from the beeches to the oaks?

To walk in a beech forest punctuated with mutations gives rise to the feeling we are all just temporary and fragile assemblages of genes, flowing through space and time. Had Darwin walked through this very forest, how might it have changed his views on “spontaneous variations” and “monstrosities” in nature? My own multiple visits to this remarkable forest of mutants brought out both the artist in me (how do you photograph them to best effect?) and the scientist (what has been written in past, what are the current theories, and what remains to be researched?). What began as a chance encounter in the snowy Arnold became a decades long hunt for plants and answers. I have little doubt that future researchers with new methodologies will return to these hopeful monsters to make new discoveries. Carriere’s words of 1864 still ring true: “a riddle to the scholars, a challenge to all plant theories.”

Rob Nicholson worked for three New England botanic gardens, undertaking over thirty plant collecting expeditions for collections building, conservation, and medical and botanical research, and making 1,920 wild collections for the Arnold Arboretum.


Bierne, J. 2017. Reversions of Faux de Verzy in European beeches: from observation to the formulation of the genetic process. RenDez-Vous Techniques, 56, pp.67–74

Carrière E. A. 1864. Les hêtres monstrueux de la forêt de Verzy. Revue Hortic., 1864: 127–131, fig. 12.

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Mićić, N., Travar, N., Gidas, J.D., Bodružić, S., Ilić, P., Hajder, Đ., and Đurić, G. 2018. Inheritance of type of tree habit in vilina bukva beech population from Čajnice. АГРОЗНАЊЕ, p.299.

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From “free” to “friend”…

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