The genus name Juglans derives from the Latin phrase Jovis glans, meaning “Jupiter’s nut,” reflecting the high value attributed to the fruit in antiquity. The species name regia means “royal,” highlighting the importance and esteem of the tree since ancient times. It is considered one of the most significant fruit trees of the temperate zone.

Walnut is a deciduous tree belonging to the family Juglandaceae. Its natural distribution extends from the Balkans and Southeastern Europe to Central Asia and the Himalayas, while today it is widely cultivated in many parts of the world, including Greece, to produce highly nutritious nuts.

The tree can reach a height of 15–25 meters, developing a large, strong trunk and a broad, rounded crown. The bark is greyish brown and becomes deeply fissured with age. The leaves are large, compound, pinnate, consisting of 5–9 ovate leaflets that release a characteristic aroma when crushed.

Flowering occurs in spring. The species is monoecious, bearing male flowers in pendulous catkins and female flowers in small groups on young shoots. The fruit is a drupe with a fleshy green husk and a hard shell, inside which lies the edible seed, the walnut kernel.

Walnut thrives in temperate climates with mild winters and cool summers. It prefers deep, fertile, well-drained soil with adequate moisture. It is sensitive to late spring frosts, especially during flowering and fruit set.

Propagation is mainly carried out by grafting onto walnut rootstocks. The tree grows relatively slowly in its early stages, but it is long-lived. It may be affected by fungal and bacterial diseases, as well as insect pests that impact fruit and foliage.

The walnut has high economic value due to its nuts, which are rich in fatty acids, proteins and trace elements and are widely used in human nutrition and the food industry. Its wood is also highly valued in furniture making and woodworking, while the tree is additionally used as an ornamental species in large landscapes and agricultural settings.