The Willow: Pioneer at ONS BUITEN

19 september 2025

At ONS BUITEN, you can’t miss them: the willows. At first, you might get the impression that only willows grow here. But in between, there are many other species to discover. The willows were planted not just for their beauty, but because they are pioneers.

Pioneers on clay soil

The soil at ONS BUITEN is in its pioneering phase: hard clay without the spongy structure we would like to see, which would allow other trees to take root properly. The willow is a typical pioneer on clay soil. We are therefore in the “willow stage” of natural succession.

How succession works

Succession occurs naturally. First come the pioneers, followed by other species that benefit from the conditions created by the pioneers. Everything then develops towards the so-called climax phase. The willow plays a key role in this. It provides partial shade and shelter from the wind, roots through the hard ground and makes the soil more aerated. When pruned, the willow releases growth hormones at the roots, which other plants can benefit from. 

Pruning to help growth

We prune the willows in summer, when they are covered in young green leaves. We harvest the branches and leaves, chop them up and use them to create a mulch cover. This allows us to give the energy and nutrients from the willow to the soil, which becomes increasingly airy and spongy. This also has a double effect: pruning above ground causes the roots below ground to die off. These then decompose, leaving tunnels in the soil, which improves the soil structure. Pruning also releases more growth hormones. In this way, the willow stimulates not only itself, but also the plants growing around it.

Space for the next layer

If we did not harvest the willow branches, a willow forest would naturally develop. By harvesting regularly, we create space for species that would normally only appear later in the succession process, such as oak or fruit trees. These trees, which form a second layer, grow more slowly. Thanks to all the work done by the willow and our pruning, they can develop more quickly. 

Different willows, different roles

At ONS BUITEN, we mainly use goat willow and white willow. These are distinct pioneers: they require full sun and eventually succumb when taller species, such as oak trees, block the sunlight. Once the oak tree is large enough, the willow simply cannot return after pruning. In this way, it passes on its place to the next phase in the succession.

Other willow species, such as the goat willow or white willow, behave more like permanent trees. They can grow into large specimens, with the main trunk remaining intact for much longer.

From willow to woodland

For the first two to three years, we mainly work with willows. Only then do we plant fruit trees and forest trees among the willows.

In this way, the willow forms the foundation for what is to come: a living system that is constantly changing and developing layer by layer.