[Ko Gyu-hong's Trees and People] Instead of Angry Thorns, Green Leaves... 40 Years Living in Korea Must Be Comfortable

<11> The Secret of Tree Survival

Goh Kyuhong, Namu Columnist.

The first life to arise on this land was the tree. On Earth, which was formed 4.5 billion years ago, life initially emerged in the ocean about 3 billion years ago. This is an unimaginably long time for Homo sapiens, who have only existed for about 250,000 years. After this vast period of silence, life finally took its majestic first step onto land 400 million years ago. Life forms that emerged as plants became the foundation for the myriad life forms on this land.

All trees on this land today bear the primordial traces of 400 million years of life evolution. Observing trees is therefore no different from tracing the history of survival strategies that life has painstakingly developed to endure. Among the various tissues of trees, there is a special tissue created to coexist with other organisms: thorns. Thorns are the result of trees transforming parts of their bodies into energy-consuming structures to survive. Most trees that have grown thorns are especially useful as food sources. Trees with tasty leaves and tender branches, which are good food for herbivores, protect themselves from being eaten by animals by growing tough thorns to block their approach. This is a survival strategy that trees have learned on their own over many years.

The Eucommia tree, belonging to the Araliaceae family, is such a tree. People enjoy eating the young shoots of Eucommia branches, which they call ‘gaedureup’. They boil them and dip them in chili sauce, fry them, or dry the tender leaves to brew as tea. Even more useful is the bark of the stem used when making ‘dakbaeksuk’ (boiled chicken soup). Chicken soup boiled with tender Eucommia branches tastes savory and mild and has certain benefits for arthritis and lower back pain. Although commonly called ‘eomnamu baeksuk’, the tree’s actual name is Eucommia.

For animals, the young shoots and tender branches of Eucommia are also good food. Consequently, Eucommia suffers hardships where its leaves, stems, and branches break even before it fully grows. In response, the tree fiercely grows thorns to survive. It has evolved to block the approach of both humans and herbivores.

Thorns growing all over the plant body are a distinct characteristic of Eucommia, but large Eucommia trees do not have thorns. This is intriguing. When the tree grows large enough that herbivores no longer pose a threat, Eucommia gradually sheds its thorns. Once it roots deeply, thickens its trunk, and grows tall, it can protect itself without thorns. There is no need to expend energy transforming leaves, branches, and bark into thorns.

The gradual change of a tree that once grew thorns to escape survival threats but then loses them when placed in an environment free from such threats is astonishing. It is as if the tree, with high intelligence, observes the surrounding environment and wisely devises a response strategy. It is truly mysterious.

The full appearance of the Caspian zelkova tree.

Caspian Zelkova Tree Native to Iranian Desert
Brought to Cheollipo Arboretum in the 1970s and Cultivated
Armored with Fierce Thorns up to Camel’s Reach
After 40 Years Without Threat, Green Leaves Sprout

At Cheollipo Arboretum in Taean, Chungnam Province, there is a special tree that was brought in during the 1970s and has been carefully nurtured ever since. It is a tree native to the desert region of Iran. Initially called ‘Iran Zelkova’, the recent national standard plant list recommends the name ‘Caspian Zelkova’. Of course, it is still not a commonly seen tree in Korea.

Like Eucommia, the Caspian Zelkova heavily arms itself with fierce thorns to protect itself and lives in the desert. This tree belongs to the legume family and is a type of tree we call ‘Zelkova’. The Zelkova trees growing in Korea also have nasty thorns on their trunks and branches, but the thorns of the Caspian Zelkova are particularly vicious. The angry thorns are so dense on the trunk and branches that it is impossible to approach.

The thorns spread from the base of the trunk along the entire branches. In the desert, where food is scarce, the tender branches and leaves of the Caspian Zelkova are an excellent food source for camels, which are key figures in the desert landscape. The tree’s primary threat in the desert is camel attacks. Ultimately, the tree grows thorns to prevent camels from approaching. Without thorns, camels would indiscriminately devour everything from leaves to young branches. Although the tree must produce nutrients through photosynthesis to grow, survival was the priority. It grew thorns before leaves. For a tree with leaves and branches favored by camels, this was an unavoidable fate.

However, such dense thorns are not found above a certain height. It is not an exaggeration to mistake the lower and upper parts as completely different trees. Moreover, the height where the thorns stop is precisely horizontal, as if measured with a ruler. This boundary corresponds to the height of a camel’s muzzle when it stretches its long neck.

There is no need to grow thorns beyond the reach of a camel’s mouth. Growing thorns above the height unreachable by camels would be wasteful. Instead of thorns, the tree should sprout as many photosynthetic leaves as possible. This is the same principle as the older Eucommia tree shedding all its thorns and becoming smooth. The tree has learned through long experience the exact height of camels and only grows thorns up to that height.

The fierce thorns of the Caspian sumac, growing thickly up to the height of a camel's snout.

Charles Darwin’s Book 'The Power of Movement in Plants' Studies Survival Secrets
Tree Memory and Judgment Show Animal-Level Intelligence

Thanks to its unique thorns, the Caspian Zelkova has become a landmark at Cheollipo Arboretum. However, around 2010, about 40 years after settling here, the tree began to show an astonishing phenomenon. Green leaves suddenly started sprouting where dense thorns had grown. At Cheollipo Arboretum, there is no need to protect the tree from camel attacks. Therefore, it does not need to grow thorns. The tree accurately recognized this. This is a result anyone could easily imagine. After living about 40 years in a protected arboretum without camel attacks, the need to grow thorns disappeared.

This raises a question: How did the Caspian Zelkova know? We need solid evidence. The question inevitably arises: ‘How does the tree remember the 40 years it has lived?’ Does the tree have memory? If it does not, does it record somewhere and check one by one?

The questions continue. Assuming the tree remembers all 40 years of its life, it also judged that since there were no camel attacks during that time, camels will not come in the future. Where did this astonishing memory and judgment ability come from? Memory and judgment are known to originate from the brain. But how does a tree without a brain remember and, based on that mysterious memory, make wise judgments?

In fact, the first person to ask this question was Charles Darwin (1809?1882). After completing ‘On the Origin of Species’ (1859), Darwin focused on plant research. He co-authored a book with his son titled ‘The Power of Movement in Plants’ (1880). This translated work is the result of efforts to find the source of the remarkably wise power plants show in their survival processes despite lacking a brain. Darwin, who explored the secrets of life, was curious. The life of plants seemed very intelligent, and he wanted to know the origin of this. So Darwin conducted various experiments. After long experiments and research, Darwin concluded in this book: “Plants have intelligence above that of lower animals.” He did not call it ‘intelligence’ originating from the brain but used the term ‘intelligence’ in a broader sense. If translated, it could be called ‘wisdom’?an ability attributed to plants. Although he did not find a brain, he indirectly expressed that plants clearly have abilities comparable to intelligence known to come from brain activity.

The memory and judgment of a tree that remembers the thorns it grew to survive and manages a more peaceful and abundant life looking far into the future is increasingly astonishing. ‘Wisdom’ comparable to ‘intelligence’. This is the survival secret of trees that live longer than Homo sapiens beside Homo sapiens.

Tree Columnist