Walnuts: stone fruits or nuts?
Everyone, whether plant-loving or not, associates the walnut tree with its healthy, tasty fruits - the walnuts. But are they stone fruits or are they real nuts?
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Traditionally, walnuts were considered to be stone fruits in botany. However, a thesis published in 2006 at the Ruhr University Bochum showed that walnuts are in fact real nuts. The shell is the decisive factor: Put simply, a nut must be a closing fruit with a seed and a hard shell. The hard shell is formed from the carpels and cannot open by itself. All of this is the case with walnuts.
From Hydrojuglone Glucoside to Juglone
Another specialty of the walnut tree is the so-called juglone. The water-soluble hydrojuglone glucoside is found in the leaves and fruits of the plant, which is leached into the soil. There it is converted to juglone by bacteria.
Juglone is the simplest naturally occurring dye. It has an inhibiting effect on the germination of other plants. That is why there is only a small amount of undergrowth in the walnut tree.
In technical terminology, this phenomenon is called "allelopathic effect". This means that one plant is chemically influenced, possibly impaired, by another plant.
Leaves rich in tannins against insects
The walnut tree has particularly tannic leaves. So these degrade more slowly than other leaves. As a result, they are not really tasty for many insects.
Nut trees are generally assigned the characteristic of keeping flies away (driving away). For this reason, they are often found in the courtyards of farms - next to the dung heaps required there. In this case, walnuts and other nut trees serve as a protective shade and enable relaxed sitting.
Sensitive to cuts due to the strong flow of juice
Another special feature is that the walnut tree is very sensitive to it Cutting measures reacts - especially in spring, autumn and winter.
When cutting in spring, an extremely strong and long-lasting flow of sap occurs - often referred to as bleeding to death. This can cause massive damage to the walnut tree.
To avoid such a scenario, you should only prune your walnut tree in late summer (August, September) whenever possible. The tree sap is limited in these two months. In addition, wound healing is faster and healthier after a late summer incision.
