Epigenetic Memory in the Spruce Tree

Foresti covers 37% of Norway’s combined area, almost half of which is made up by the tree species called Norway spruce. The rest consists of mostly pine and birch. It is therefore only natural that spruce forests should feature so heavily on black metal album covers and lyrics. The extreme music genre of black metal, as we think of it today, was birthed in Norway. Although it could be said that its place of origin was accidental, the subsequent use and appropriation of that place’s topographic features was not. Since its inception in the early nineties, the genre has spawned countless bands across the globe, many who take on its misanthropic ethos, but also a deep reverence and respect for nature. Within black metal’s aesthetic, photographs of ominous black tree lines and lyrics about disappearing into the depths of the forest abound – it is almost as if the spruce tree has become its own character in the mythology that black metal has become.


The Learned Pig


Artist Una Hamilton Helle in conversation with molecular biologist Carl Gunnar Fossdal

Carl Gunnar is a Research Professor in Molecular Biology at the Norwegian Institute of Bioeconomy Research (NIBIO), whose research looks at epigenetic memory in Norway spruce. Una is an artist whose practice investigates properties of place and nature, and whose project ‘Becoming the Forest’ looks at this through the lens of black metal. Seeing similarities between their practices, she spoke to Carl Gunnar about his findings in the seeds and growths of Norway’s most common tree species, and wondered whether these findings could be read as scientific allegories of age-old ideas about trees as holders of wisdom, permanence and memory, or vice versa.

Below is a lightly edited version of an interview featured in Becoming the Forest #2, a publication which treads the backwoods of black metal, folklore, landscape and place making, as seen through animism, grief and molecular biology.

Epigenetic Memory

Una: I became interested in your work as a molecular biologist when I read an article where you spoke about spruce tree seeds as having ‘memory’. It was explained that the seeds, although moved to a different climate than where they originated, would ‘remember’ the climate from which they came. Could you expand a bit more upon this project and your research in the area? And for somebody unfamiliar with the study of epigenetics and molecular biology, could you give an overview of what these sciences are in layman’s terms?

Carl Gunnar: Epigenetics represent aspects of an organism’s behaviour (phenotype) that can’t be explained by genes alone (genotype) – the classical basis of evolution. Flexibility in the genes is caused by epigenetic mechanisms. Epigenetics is the reason why having a gene for a certain disease doesn’t necessarily mean you’ll get the disease, as how that gene is actually being expressed and its impact on health is dependent on small reversible chemical or structural modifications to the chromosomes. DNA can be methylated, and the histones proteins that scaffold the DNA into chromosomes slightly modified. These modifications impact on whether a gene is expressed, or how strongly it is expressed, thus changing the phenotype (i.e. the behaviour of the organism). Such epigenetic modifications give the organism greater flexibility to respond to (and sense) changes in the environment and is a type of (molecular) memory.

The way you describe epigenetic memory is almost right, Una. Spruce trees do not remember the place they originated from, but rather the environmental conditions under which they were formed. The conditions in a given place change from year to year and so does the (epigenetic) impact on the developing embryo.

The spruce forest dominates the landscape, growing dense, acidifying the soil beneath it, and… displacing other life forms.

Epigenetic memory in Norway spruce is caused by the surrounding environment when the embryo in the seed develops. For instance, temperature increase may cause permanent change to the tree’s growth cycle and this change will be remembered as long as the tree lives. Epigenetic memory in Norway spruce affects its bud phenology, which is how fast it breaks bud in the spring and forms new buds in the autumn. Spruce trees do not tolerate frost during new growth periods, so the correct timing of bud burst can be a question of life or death if there are late spring frost incidents. We don’t yet know if some of this epigenetic memory is passed on to subsequent generations of trees.

I also study another phenomenon coined ‘acquired resistance’ in spruce. When a tree survives a pathogen infection, or severe stress, a defense memory called ‘acquired resistance’ can be induced. Acquired resistance (also called priming) is the ability to react more strongly and effectively to a challenge the second time around – weakly analogous to when a person is vaccinated (although plants do not have circulating blood with B-cells that produce antibodies like we do!). Acquired resistance also requires an epigenetic mechanism but these ‘memories’ are more short-lived and last only 1–3 years in trees, rather than a lifetime.

Epigenetic memory most likely makes these trees able to adapt more rapidly to changes in their environment, which can be critical for survival if there are rapid changes such as those associated with global warming and ice ages.

Epigenetic Memory

Una: My work looks to Norwegian folklore for inspiration, where romantic and animistic interpretations of Nordic nature play an important part. In our folk tales, it is said that large stones may once have been trolls caught unaware by the sun, and folkloric characters such as Nøkken and Fossegrimen represent personifications of lakes and waterfalls (or perhaps the personification of the danger those places can represent).

I am interested in the spruce tree because it seems to have taken on this symbolic quality within black metal. Tree lines (and they are always spruce tree lines) are depicted heavily on album covers, the forest is often portrayed as the main protagonist in song lyrics, and forest spirits are conjured through sounds and liner notes. I believe this came from a subculture that, when it started out, was trying to unearth something that was quintessentially Norwegian. Whereas many musical subcultures are about rejecting society, black metal became very much about searching out, or ‘rediscovering’, elements of a culture that one could feel a sense of belonging to.

Naturally, as there is so much of it in Norway, and as it is so embedded in our cultural traditions already, nature became one answer. At the same time, it is almost like the landscapes depicted in black metal are visual representation of the music: jagged mountain peaks, pointed tree tops, always black and white, hostile and dark… Do you recognise this reading of the forest and the spruce tree?

Carl Gunnar: Yes! Spruce trees are very tough and resilient, particularly in the deep, cold and dark winter. The spruce forest dominates the landscape, growing dense, acidifying the soil beneath it, and it largely dictates what other plants may grow alongside it, displacing other life forms. However, in late spring and close to summer it is transiently light green, soft and welcoming in the long bright days with new growth, far from that darkness. Migrating birds find shelter, build nests and raise their young in the tree crowns. The character of Norway spruce changes dramatically with the seasons, from my perspective.

To me the tree is a reflection of how its inherited genes and its environment interact with (and impact) each other. My focus also tends to be on an individual tree, and on how trees differ from each other, rather than on the forest as a whole or as one (connected) thing.

Epigenetic Memory

I also want to know how genes are regulated inside the various cell types in a tree. Reproducibility is important, so we use clones to see if the same changes happen in all members of a clone (i.e. individuals with the same genes but existing as separate individuals, like rooted cuttings or shoots originating from the same cell culture). I view members of a clone as genetically identical, but when epigenetic changes occur (as in the case of epigenetic memory) even members of the same clone show differences and emerge as something separate and unique – the obvious human analogy is when identical twins show significantly different behaviour or a different fate due to epigenetic changes in their DNA.

Norway spruce is a tough species to work on from both a scientific and laboratory point of view, as it is recalcitrant to extract DNA and other molecules from. It has seven times more DNA in its chromosomes than a human, long generational times, and delayed flowering (it can start producing seeds only after fifteen years, although usually this happens much later), and it reaches massive sizes. This makes it very challenging to do genetic research on trees compared to herbs and plants smaller in size and with less time between generations.

As scientists we are not yet able to completely rule out that some plants may have some level of consciousness.

The animistic aspects in my work are not apparent as no spirits are considered to inhabit our trees (as in folklore or folk religion). If trees or rocks have a spiritual essence, it is in the realm of art and beyond the scope of my work, and is likely defined by the ‘eyes’ or ‘wish’ of a conscious beholder. There is no separable soul/spirit that may impact the body in my view, but indeed during epigenetic memory the environment impacts on and modulates how the genes are expressed, and imprints a lasting impression, so there is a (far-fetched) analogy.

However, as scientists we are not yet able to completely rule out that some plants may have some level of consciousness, although this is probably a consciousness very different from that in humans and other animals. People have had very different ideas about consciousness in animals through the ages. For example, some vegetarians won’t eat animals because they feel pain or because they have a higher level of consciousness (like dolphins and other whales). There is no indication people will ever feel the same way about plants as about animals, even if the felling of majestic trees and clear-cuttings in forests can get people’s emotions going at times.

Epigenetic Memory

Una: I enjoy the idea of the Norway spruce as a dominant (over-powering and acidifying) life form and a recalcitrant tree. The definition of recalcitrant is ‘having an obstinately uncooperative attitude towards authority or discipline’. This chimes well with black metal’s attitude, if you ask me… The spruce seems to be very much aligned with giving two fingers to authority, but then it also has this menacing and overpowering vibe, a bit like a mean older sibling.

I was also interested in the idea of priming or acquired resistance, as an extra defensive ‘back-up plan’. I guess as a tree you have no choice but to stay put so you are going to fire all your defence mechanisms towards any threats. Am I right in thinking that the Norway spruce is one of the trees with the most developed form of resistance? You describe the process it uses to survive and also ‘take over’ the topography – is this because other trees just aren’t as dominant? With its resilience in mind, what are the current thoughts on how the Norway spruce will survive in the future, with possible climate change-induced temperature rises? Are we looking at a future world filled with spruces as a dominant force?

Carl Gunnar: Norway spruce has both constitutive (continuous) and induced defences. The constitutive defences include the dead outer bark, specialised cells and channels of resin. The inducible defences are turned on when these constitutive defences are breached by a pathogen. The inducible defences can activate genes and the production of enzymes (proteins) that can then directly attack the pathogen or defend the tree by producing protective chemicals and increased fortifications of the plant cell walls. Its defence system has been compared to a medieval castle with a watery moat and rings of solid walls, with armed sentinels on the lookout for enemies. Priming is a temporal (memory) layer that adds to this defence, as previous exposure will set the defence system at a higher state of alert and the tree will be more equipped to withhold an attack.

In Norway, the relationship to the forest is one of dark mystery, almost spiritual.

Although we are studying priming/acquired resistance in spruce, we do not yet know enough to say if they have the best defence mechanisms in the plant world. We do know that their primed defences are more long-lasting than in any other plant studied so far – after all, these defences can keep a tree alive for up to and beyond 5,000-year life spans – but we are also some of the few who are looking seriously into this in long-lived plants. Most scientists tend to study more short-lived and non-woody plants, as results are quicker to obtain when studying shorter life spans.

Una: Norway is full of trees and obsessed with wood. On the one hand, it seems to me that the relationship to the forest is one of dark mystery, almost spiritual. Black metal relates to it this way – as a place where you can fully be yourself – both a place of subversion and one where romantic notions of what it means to be Norwegian are explored. On the other hand, there is this very pragmatic and practical relationship to trees as a resource and a tool. We use them to build with, to make paper out of, to burn… The fact that a book about how to chop and stack wood was a bestseller in Norway says it all, really. I’d be interested to hear your views about this idea of trees and nature as a symbol of ‘Norwegianness’. I would assume that through your research you relate to it in a very different way?

Epigenetic Memory

Carl Gunnar: The fact that Picea Abies is synonymous to ‘Norway spruce’ says it all, doesn’t it? My fellow scientists from other countries (Russia, Sweden, Finland etc.) are envious that the common name used is Norway spruce, named so by the British due to exports to the UK in the old days. This is for good reasons, as this tree species is in most parts of Norway quite a recent immigrant (<2,000 years). So even as a scientist I also feel connected to this tree species and its ‘Norwegianness’. Having worked with Norway spruce since 1995 and seeing its inner complexity and beautiful ability to respond and adapt, I am getting pretty obsessed with it myself. It is our preferred forest species to study and our most important tree species economically and ecologically.

I have a lot of respect for this tree, as it is surprisingly well adapted and able to thrive in most parts of the country, despite being such a recent evolutionary settler. In the winter, when it is at its most resilient, it can even survive immersion in liquid nitrogen ( 196°C) so it is extremely cold tolerant. In the late spring however, the new buds may not even tolerate -1°C, which can result in new growth wilting and dying. Norway spruce is both extremely tough and subtly vulnerable, depending on what part of the yearly (growth) cycle it is in. It also has both male and female characteristics. The individual tree has both male and female ‘flowers’ (reproductive organs), so any given tree can be both a father and a mother to a new seed, although even if it has both reproductive organs ‘selfing’ is not common.

Una: Many black metallers have spoken about how the surrounding landscape feels like a direct connection to, and the only stable element of, a distant past, characterised by Norse mythology and Scandinavian folkloric tradition. From a biological perspective, I am sure you would disagree with the use of ‘stable’ in that description! In black metal, however, it is almost as if the spruce tree has become this topographical monument; a symbol of a longed-for past that people are trying to connect to – maybe you could say it was almost functioning like a topographic totem pole. The idea, therefore, that trees and their seeds have a type of memory is therefore a very nice allegory to me. Could you outline how this ‘memory’ works in practical terms – how far back does it reach and what do we know about the spruce tree’s resilience? I read that the spruce tree has been around for 300 million years, whereas modern man has been around for 200,000. Is there something we could ‘learn’ from the spruce and its adaptability?

Carl Gunnar: I agree with the notion that spruce and the landscape connect us to the past, but not in a romantic, uninterrupted or unaltered sense. Spruce was probably here in large numbers before the ice ages and is now reconquering the country.ii The landscape, though altered, is probably much like it was a million years back, partly covered by the beloved snow and ice. Being this far north also allows for great day length variations, which give rise to the particular light qualities we have throughout the seasons. I view man as part of nature and believe that no forests are truly artificial – nature will find its way. The fact that man and other animals (and plants) shape the landscape and the number and types of trees in it, is only natural to me.

The fact that man and other animals (and plants) shape the landscape… is only natural to me.

To give an example: elephants remove trees, leaving open grassland landscapes suitable for its major feedstock, much like humans burn the forest and farm special grass varieties like wheat and other grains. Man has shaped most of the forests in Norway trough massive plantings of spruce in almost ominous proportions. My predecessors approached the task of planting and spreading the forest with an almost religious zeal, and our institution’s previous motto was ‘to clothe the land in forest’. This came from an almost social collectivist idea that the forest would create jobs and wealth for foresters, and was a major force in how we viewed the country’s relationship to productivity and natural resources. Thus, Norwegian forests truly reflect the activity of man, past and present.

Epigenetic memory works as a way to adapt rapidly, without needing to select specific genes. It gives extra flexibility to cope with sudden changes in the environment. It gives the trees the time to survive to maturity and beyond, thus allowing also for natural selection to occur. We do not know how long epigenetic memory may last in spruce but it is certainly theoretically possible that it lasts many generations. In humans, there are reports that it is seen in grandchildren, although in principle, all such epigenetic marks can be erased at any time.

Epigenetic memory

Una: It is interesting to hear how much spruce is formed by, and adapts to, external forces like the environment. I am interested in how much of a role landscape, surroundings and weather have in influencing the human mind, and hence the creation of artistic expressions (such as Norwegian black metal or, say, the emotionally embedded nature depictions by Romantic artists such as Theodor Kittelsen). A strictly causal relationship is easy to dismiss, as in its extreme version it is the basis for pseudosciences such as the National Socialist concept of ‘blood and soil’. On the other hand, there is definitely something in the pop theory that people’s moods are affected by the amount of light they are exposed to.

I view artistic expressions as ways of making sense of the world, but also embedding the world with meaning. Subcultures often attempt to rewrite existing societal rules, or replace them altogether, in order to give significance to our lives and substantiate our position in the world. Black metal was (and is) hostile towards the dogmas of religion, and espoused a decidedly individualistic attitude. As seems to be the fate of almost all subcultures, however, it eventually developed into a code of symbols and opinions that almost equal the rigid rules and measures of any religions it supposedly opposes… How does the world of science compare? In my mind, science represents the antidote to irrational behaviour, but then it also has to be as open as possible in order to accept any unexpected proof that arises from experiments. True or false? How open to interpretation is your line of work?

Epigenetic Memory

Carl Gunnar: Science is mainly based on experimentation, and reproducibility (the ability of an entire experiment or study to be duplicated, either by the same researcher or by someone else working independently) is considered the best way to verify a hypothesis. Science is in principle rational, but a given scientist (or group of scientists) is not necessarily always rational. Science has branched out into many disciplines and tends to become more and more specialised. The language, culture and traditions within each branch differ to smaller and greater degrees, so what you call subcultures, with very different, and even opposite perspectives, may well arise in science as well.

Established ‘truths’ can make it difficult to find new or alternative answers. Sometimes established paradigms are so dominant that they inhibit scientists from seeing better answers, and can even greatly delay radical new insights. Paradigm changes are sometimes needed for science to advance further and there can often be a strong reluctance to such paradigm changes by the establishment (i.e. leading scientists that hold the old view) and who, due to hard-headedness, do not allow themselves to see things in a new light.

For example, epigenetics is an emerging field in biology but its advent was delayed due to faulty interpretations by scientists like Lamarckiii, overstating the extent of inheritance of acquired characteristics. A much more serious setback was caused by Lysenkoiv, who pushed the concept of environmentally acquired inheritance to the extreme. To Lysenko, environmentally acquired inheritance was the rule rather than the exception. In his increasingly deluded mind, the principles of Marxism also held true in nature. Lysenko rejected classical genetics in favour of pseudoscientific ideas that stated that if a crop was subjected to the right environmental conditions, he could make it adapt no matter what genes it inhabited. He even believed he could turn one type of crop into another. Many scientists who opposed his ideas were killed because they did not conform to his and Stalin’s ideas. With time, the impact of these abysmal failures has waned and we are again able to see that there are indeed some important examples of acquired characteristics that may be inherited. We have even untangled some of the underlying molecular mechanisms that make epigenetic changes (and for these to be inherited) possible, and they are of importance in biology. Nowadays epigenetics is one of the hottest topics in biology.


This is a lightly edited version of an interview featured in Becoming the Forest #2, a publication which treads the backwoods of black metal, folklore, landscape and place making, as seen through animism, grief and molecular biology.

The publication’s London launch takes place at Nambucca, London on 22nd October with a brilliant-looking programme of talks and music.

All images and collages from the ‘Becoming the Forest’ series by Una Hamilton Helle.


The Learned Pig


i. English translation of the title: ‘Into the Deep Forests Embrace’, a track off prolific Norwegian black metallers Darkthrone’s 1993 album ‘Under A Funeral Moon’

ii. There is also some serious controversy regarding how long Norway spruce has been in Norway and Sweden. Some scientists claim Norway spruce survived the ice age in Norway, and one Swedish scientist even claims that some of the same trees are still alive to this day. However, this is not an established fact, even if it may seem so from reading Wikipedia.

iii. Jean-Baptiste Lamarck (b.1744, d.1829) was a French biologist who was an early proponent of the idea that evolution occurred and proceeded in accordance with natural laws. He is widely remembered for a theory of inheritance of acquired characteristics, called soft inheritance, Lamarckism or use/disuse theory [Wikipedia].

iv. The pseudo-scientific ideas of Trofim Lysenko (b.1898, d. 1976) built on Lamarckian concepts of the heritability of acquired characteristics. Lysenko’s theory rejected Mendelian inheritance and the concept of the “gene”; it departed from Darwinian evolutionary theory by rejecting natural selection. Proponents falsely claimed to have discovered, among many other things, that rye could transform into wheat and wheat into barley, that weeds could spontaneously transmute into food grains, and that “natural cooperation” was observed in nature as opposed to “natural selection”. Lysenkoism promised extraordinary advances in breeding and in agriculture that never came about.

Una Hamilton Helle

Una Hamilton Helle is an artist based between London and Oslo who uses images, installation, collaborative workshops and the written word to explore how we locate and create meaning for ourselves. She is especially preoccupied with nature and landscape as a subject as well as looking at how differing disciplines can overlap and have a dialogue. She recently published Becoming the Forest #2, a journal which forms part of a wider arts project about forests and black metal. She also curates and commissions exhibitions and events as part of contemporary art organisation Legion TV.