Walnut tree, a tree with many stories to tell

As this is one of the longest cultivated fruit trees in Europe, it’s only natural that there is so much to say about the walnut tree (Juglans regia). In addition to being highly appreciated for providing quality wood for furniture, its cultivation serves the production of well-known walnuts, used in food, but also in medicinal applications e.g. through its leaves.

You probably didn’t know that walnut plantation dates back 8,000 years. It is believed that this tree was planted for the first time in Ancient Greece and that it is native to the Mediterranean basin and central Asia. In fact, pollen and bark records show signs of cultivation in Italy about six thousand years ago and in Anatolia, Greece and Croatia about four thousand years ago, namely in farmlands, bordering cultivated fields, mudflats, vegetable gardens and orchards.

With a big capacity to adapt, this species can grow in different types of soils, although it grows more quickly in places sheltered from strong winds and high temperatures, which may burn its trunk. As regards its shape and size, it is a deciduous tree with a wide and branched canopy, which can reach 30 meters in height and last about 300 years.

Given this tree’s excellent quality wood that is easy to polish, it has been widely used in the manufacture of furniture, at least since the 16th century, but also to make musical instruments, among other objects. However, to get here this tree requires about 50 years of good management from an early age and this includes several  formative cuts and pruning. The goal is to achieve a trunk without defects, with five to six meters.

When it comes to cultivation for walnut production purposes, the walnut tree begins to bear fruit around the age of 7, increasing the quantity as it grows. That is, a 10-year-old tree can produce about five kilograms, doubling this amount when it reaches the age of 20 years and by the time it reaches between 30 and 50 years of age the maximum amount is 18 kg/tree.

Hidden inside a nut until harvest or when they ripen, between September and October each year, walnuts prove to be a very nutritious and tasty fruit and are a source of fibre, vitamin E and B complex, and minerals such as magnesium and phosphorus. In Portugal, a country where it is highly appreciated, the production area increased by about 92% between 2012 and 2021.

In addition to the several uses of wood and its walnuts, we can take advantage of the several parts of the tree for other uses.  See for example the natural brownish pigment, created from the shell of the walnut and the walnut itself. After being ground into a powder, it is used to colour fabrics,  makeup, and even hair.

The leaves are also used for medicinal purposes and in 2011 the European Medicines Agency confirmed the safety of the therapy of traditional applications in the case of superficial inflammations of the skin and excessive perspiration of feet and hands.

Walnut oil was initially used in street lighting but is currently an  omega-3 rich ingredient and used to make soaps and creams developed by natural and handmade cosmetic makers. In food, where it can be used as a seasoning, it is considered one of the healthiest oils.

Did you know that…

Walnut belongs to the Juglandaceae family, the same as its relatives Carya illinoinensis, whose fruit is the famous pecan, and the black walnut (Juglans nigra), both from America.

Its scientific name Juglans regia came about in tribute to Jupiter, the king of the gods in Roman mythology, for his production of walnuts and wood.

The Romans chose walnuts as a luxurious fruit and whole walnuts were found in the ruins of Pompeii among the foods that were on the table in the Temple of Isis, under the lava of Vesuvius, whose volcanic eruption happened in 79 AD.

The oldest walnut tree on record is located in Spain and is about 530 years old, far exceeding the average longevity of this species.

Among the walnut tree pests that cause the most damage are the codling moths (Cydia pomonella), walnut husk fly (Rhagoletis completa) and the leopard moth (Zeuzera pyrina), whose caterpillars dig galleries on trunks and branches. On the other hand, aphids, mites and mealybugs do not cause economically relevant damage.