Walnut trees are very popular with owners of their own garden or pasture. But when the leaves start to fall, they often end up in the flower beds or in the vegetable garden. It is now said that you should not let the leaves of a walnut tree decay in a flower bed or vegetable garden because that would be bad for the soil. Is it really true that the soil becomes acidic due to the leaves of the walnut or is that just a myth?
Leaves of a walnut tree decay more slowly
The fact is that the leaves of an oak or walnut tree should not be too abundant on the bottom. After all, they contain tannins (tannic acid) and decay more slowly than normal ?? leaves, closing off the plants / soil underneath. Lawn grass and other fine vegetation can be suffocated by it!
Chemicals negatively affect the growth of other plants
The leaves of the walnut tree contain chemicals that negatively affect the growth of other plants, a phenomenon also known as allelopathy. These substances end up in the soil from the leaves and fruits of the walnut tree and are converted by hydrolysis and oxidation into a growth-inhibiting compound called Juglon.
This creates less favorable conditions for seed germination, so that little growth activity can usually be detected under the crown of the tree. According to some biologists, the soil does not become much more acidic, but the germination of seeds is strongly inhibited. This generally applies under a walnut tree, not only because there are leaves on the bottom.
What does want to grow under the walnut tree?
But the fact that there are germ-inhibiting substances in the soil does not mean that nothing at all wants to grow under a walnut tree. Of course there are a number of plants that can continue well despite their germ-inhibiting effect. Nature is never final. But it would seem that the walnut tree’s only goal is to eliminate real competitors. Hardly any other trees or shrubs naturally grow under walnut trees. But because grass is not really seen as a competitor by the walnut tree, and there are many more grass seeds in the soil than other seeds, grass still grows reasonably well under the walnut tree.
How can one stimulate plant growth under walnut trees?
From the above it can be deduced that walnut trees live more or less in ecological competition with other plants. Any planting under a walnut tree therefore has to deal with four problems:
- if the tree has branched meadows, it naturally casts a lot of shade;
- there is a lot of competition when it comes to moisture and nutrients;
- germ-inhibiting root secretions;
- relatively slow rotting leaves.
All four points mentioned can be counteracted in a simple way so that plants that tolerate some shade are not in the way:
- prune back wide or high branches;
- provide sufficient water and fertilization;
- preferably do not sow plants;
- remove the foliage from the tree as much as possible and compost it separately.
The walnut tree in the olden days
In earlier days people were already familiar with the whims of the walnut tree, but they also knew to appreciate its good qualities. Our rural grandparents will undoubtedly remember that the walnut tree always had a permanent place in the yard: next to the house or the farm there was usually a stable or shed and usually a large walnut tree stood in front of it: not only for the produce of the walnuts , but also for the shade and the fact that the tree kept flies and mosquitoes away. A walnut tree in the adjacent vegetable garden was out of the question. People knew better at that time.