The Arboretum was created by the Belgian forestry specialist Charles Bommer in 1902 at the request of Leopold II. Spanning approximately 120 hectares, it contains around 700 exotic tree species organised in 40 geographic tree groups. Tervuren+’s Jasmin Kohl spoke to forest ranger Kevin Knevels about the state of the tree collection, strong ties with the American Chestnut Association, and wild boars.
What are the oldest trees in the Arboretum and where can you find them?
We have some sequoia and chestnut trees which are approximately 120 years old, meaning they were among the original plantings by the designer of the Arboretum, Charles Bommer. You can find the sequoia trees in the “New World”, group 7, and the chestnut trees in group 15.
What is your favourite part of the Arboretum?
I prefer the Japanese section in the Old World (Arboretum groups 38-40) because of its colours and flowers. Japan is a very volatile island, with the calm East China Sea on one side and the rough Pacific Ocean on the other. So there are a lot of climatic differences between the lower and higher zones, as well as between the east and the west of the island. It is one of the harshest ecosystems for plants, because they have to adapt to these conditions.
When you walk across the Arboretum, you see a lot of trees that are broken by wind or infested by parasites. What are the biggest challenges in maintaining the collection?

More than 120 years after its creation in 1902, we are currently in a period of transformation. This is a great opportunity to learn, and it goes hand in hand with the most exciting part of my job: reinventing. Many trees are dying, and the causes are complex: While some people immediately attribute it to climate change, particularly dry soil, the situation is not so simple. Some tree species just don’t live that long and die a natural death. Additionally, drought is not necessarily a problem in a natural ecosystem, as it can adapt to it under certain circumstances. Some people mistakenly think that nature, and thus ecosystems, are stable. However, this is a serious misconception of how nature works.
Still, several tree species in the Arboretum don’t reach their maximum size and age simply because the meteorological conditions in Flemish Brabant are less favourable for them. Why does it still make sense to maintain this collection of tree species from all over the world?
Charles Bommer designed the Arboretum to collect ecosystems, not just trees. To better understand why some tree species are struggling more than others, we invite scientists from all over the world to study the trees in their unique ecosystem within the Arboretum. This was the original purpose of the collection: to learn how exotic tree species would adapt to local conditions and evaluate the usability of those trees in afforestation projects. Today, we see that many tree species from the South are adapting better to our local conditions due to the climate change. This is an important finding, which can help us create more sustainable forests. That’s the Arboretum’s unique selling point: What’s happening here is happening in the whole world, but in the Arboretum, we can study the causes in-depth and learn from it.
Kevin Knevels has been working as a forest ranger in the Arboretum for eight years.
Moreover, the Arboretum preserves tree species that are nearly extinct in other parts of the world. Take, for example, the American chestnut: It originates from the East Coast of the US, but due to a deadly blight (a fungus) introduced by Asian chestnut species, adult American chestnuts have been extinct in the US for decades. But not in Tervuren! With 14 specimens, the Arboretum hosts the largest number of adult American chestnut trees in the world. This is why the American Chestnut Foundation visits Tervuren every year to study these remaining specimens and to conduct DNA research. To preserve various tree species, we also collect their seeds and send them for free to tree nurseries.
What about the wild boars? Currently, you see a lot of burrowed areas in the Arboretum…

Wild boars are a relatively new presence in the Arboretum. They first appeared four years ago. As long as the ground is soft, they “rootle”, meaning they turn over clods of earth with their snouts to eat roots, rhizomes, beetles, and worms, for example. This makes them the biggest bio-engineers in the forest. They are typical forest animals and are actually good for the forest because they eat beetles, spread seeds, and help the forest in this way. Wild boars only become a problem when there is an overpopulation, which is currently the case.
To prevent them from damaging young seedlings, we use homemade pepper spray or homemade chilli oil, which works very well. For now, this is enough to limit the damage to the Arboretum, so we haven’t had to shoot any to control the population. But this might become necessary in the future.

Is there a risk of encountering a wild boar when you’re walking through the Arboretum?
No, wild boars are usually active at night and early in the morning. But even if you’re in the Arboretum during these times, it’s unlikely that you’ll see them: They generally avoid humans and due to their strong sense of smell and hearing, they can detect your presence long before you can see them. They are not aggressive as long as you use common sense: never approach them, especially when they are with their young.
“Sustainable forest management” is applied to the Arboretum. What does this mean concretely?
This management approach involves practices with a low impact on nature. For example, we use electric engines instead of gas engines, and we avoid plastics and pesticides. To protect young trees from animal damage, we use sheep wool, as its smell discourages animals from approaching young seedlings and damaging their trunks or biting off their tops.
Are you seeking volunteers?
Yes, there are various ways to get involved with us: from planting or measuring trees, counting birds of prey, collecting seeds, to taking photos and guiding visitors through the Arboretum. The volunteer work is organised into four different working groups: 1) Nursery, 2) Guides, 3) Communication, 4) Dendrology and Research. Anyone interested can register via this online registration form to join us! We meet every second Tuesday afternoon and every third Saturday afternoon.
Photo copyright: © Koninklijke Schenking/Donation Royale. Kevin Knevels. Arboretum Tervuren. Photo: F Raevens. All other photos: Jasmin Kohl.
More information: www.arboretum-tervuren.be






















