From seedling to tree - An interview with climate forester Jan

With Planted, we plant trees throughout Germany to provide an impetus for the mixed forest of the future. By this, we mean maintaining at least three different tree species that can cope well with extreme weather events as a result of climate change in one forest area.

In this interview with our climate forester Jan, we want to talk about how such a planting takes place, when is the best time to plant trees, which tree species are climate stable and what makes the forest so worth protecting.

Planted has been planting trees in Germany since 2020, and now in areas all over the country. Where do the seedlings that are planted in the ground come from?

We obtain our seedlings from nurseries. When selecting our partner nurseries, we pay attention to regionality, so that there is already experience in the forest areas. 

And how is it decided which tree is planted in which area?

Which trees are planted on which area depends on the area itself and its conditions: What is the climate on site, what are the soil conditions, is the area flat or on a slope? We foresters call this the conditions of the "site". In addition, we also check which trees are already growing on or near the area and could thus come back on their own. 

In some cases, customers' climate profiles also show trees that have not yet been planted and are depicted as seedlings. What is this all about?

That's right, not all of the trees displayed on our Planted Partners' climate profiles are already planted. That's because we use a specific season for planting. We start in November and plant until the end of March. During this period, it is cold and it doesn't bother the little trees as much to be moved. They are in a kind of hibernation and do not resent us planting quite so much. It is also important that the soil is supplied with water so that the roots grow well. You know it from repotting at home, there must also be watered. And in the autumn / winter / spring months it simply rains more. 

‍Hibernation? That sounds very lively. Can you explain it in more detail?

Hibernation can also be described as a kind of vegetation dormancy: The tree has shut down its life systems to the bare essentials. The trees have even stopped vital photosynthesis and shed their leaves. The roots have turned off contact with water and the little tree is in a kind of rigidity. If we would plant the trees also during the summer, they would have big problems to grow. The contact to the water already exists then and would be separated from us. It would be very difficult for the tree to get back into contact with the soil and water - if there is still water in the upper soil layers in summer. 

And how exactly is the little seedling now put into the ground?

First, the upper layer of soil, called the humus layer, is pushed aside. Then a hole is dug, which must reach as deep as the longest root. The entire root ball must be in contact with the mineral soil so that the nutrients can be absorbed and the connection to the groundwater is successful. The hole is then filled again with the individual soil layers. Therefore, when digging the planting hole, it is important to take care not to mix the soil layers too much.

In the first year and a half, you have already planted over 170,000 trees. How do you implement the plantations? Do you have partner organizations?

We work closely with the forestry offices and the district foresters there. In general, we now have a good network and enjoy enormous trust from the foresters. The fact that I studied forestry myself and have been in the forest since I was a child means that cooperation is very good for both sides. We simply speak the same language - that of the forest.

Most of the trees are planted by real professionals from the forestry offices and tree nurseries, as we can't do it alone. We are currently planting three soccer pitches of forest per month - we simply need support. In addition, we plant under guidance with companies in team events and the entire Planted team also knows how to plant the trees in the ground - a matter close to my heart.

When is a tree fully grown? Is there a point in time when you can say: "Now the tree is storing CO₂ properly?

Trees grow in three directions: To the sky, to the width and to the ground. You always have to keep that in mind. And depending on the tree species, one direction is preferred. The fir tree, for example, first develops a huge root before it begins to shoot upwards. However, we humans probably most often understand the term "mature" to mean growth in height. At 30 to 40 meters, a tree in Germany is mature in height on average. 

About CO₂ storage: This is what the tree does in the wood. Approximately one ton of wood stores one ton of CO₂. Everyone knows the annual rings of the tree, by which you can count how old the tree is. The annual rings are always similar in thickness, but the circumference increases from year to year. It is therefore simple mathematics that the tree stores little CO₂ as a seedling and then more and more as it ages. 

What do you think is so special about planting trees? Can you explain why the forest is so important?

As already mentioned, our forest stores CO₂ and is one of the most important natural carbon sinks. But the forest is so much more. It provides a habitat for countless animals and other species, stores and filters our drinking water, serves as a noise barrier, filters dust and other dirt particles from the air, has a cooling effect and produces oxygen. In addition, wood is also an important and above all sustainable raw material: because every piece of furniture made of wood continues to store the CO₂ absorbed as a tree. But it is not only from wood as a resource that we humans benefit. Especially during the Corona pandemic, each and every one of us noticed how much the forest serves us as a recreational space - even studies have proven that.

I think this is a good illustration of what makes forests so important for all of us. Regardless of whether we are planting new trees and thus providing impetus for the mixed forests of the future or whether we are protecting existing forests. With Planted, we have set ourselves the task of supporting our German forests, making them fit for climate change and preserving them for future generations. Because that is our mission with Planted: we want to make the future sustainable - whether in terms of forests or the decarbonization of companies.