The walnut tree differs in many properties from other fruit and other trees. In this article, you will learn about the most important characteristics of the walnut, which was voted tree of the year in 2008.

Walnuts were considered a drupe until 2006

Walnuts: drupes or nuts?

Everyone, whether they have an affinity for plants or not, associates the walnut tree with its healthy, tasty fruits - the walnuts. But are these stone fruits or real nuts?

Walnuts were traditionally considered drupes in botany. However, a diploma thesis published in 2006 at the Ruhr University Bochum showed that walnuts are indeed real nuts. The shell is the deciding factor: Put simply, a nut must be an incipient fruit with a seed and a hard shell. The hard shell is formed from the carpels and cannot open independently. All this is the case with walnuts.

From hydrojuglong glucoside to juglone

Another special feature of the walnut tree is the so-called juglone. The leaves and fruits of the plant contain the water-soluble hydrojuglong glucoside, which leaches into the soil. There it is converted to juglone by bacteria.

Juglone is the simplest naturally occurring dye. It inhibits the germination of other plants. This is why there is only a small amount of undergrowth on the walnut tree.

In technical terms, this phenomenon is called "allelopathic effect". This means that one plant is chemically influenced, possibly affected, by another plant.

Leaves rich in tannin against insects

The walnut tree has leaves that are particularly rich in tannins. These decompose more slowly than other foliage. As a result, they are not really tasty for many insects.

Nut trees are generally credited with keeping flies away (repelling them). For this reason, they are also often found in the courtyards of farms - next to the manure heaps required there. In this case, walnuts and other nut trees serve as protective shade and enable relaxed sitting.

Sensitive to cutting due to strong sap flow

What is also special is that the walnut tree is very sensitive to pruning measures - especially in spring, autumn and winter.

When cutting in spring, an extremely strong and long-lasting sap flow occurs - often referred to as bleeding. This can massively damage the walnut tree.

To avoid such a scenario, you should only prune your walnut tree in late summer (August, September). In these two months, the tree sap is limited. In addition, wound healing after a late summer cut is faster and healthier.

Category:

Vegetable garden