Common walnut - leaves - October 2018

Walnut tree is a deciduous plant that belongs to the family Juglandaceae. It originates from Central Asia and Europe. Walnut tree grows on fertile soil, in areas that provide enough moisture and direct sunlight. According to some researchers, walnuts are part of human diet nearly 10 000 years.

People consume 2.5 million tons of walnuts each year. Most commercially available walnuts originate from California, which is the greatest producer of walnuts in the world.

Walnuts have high nutritional value and act beneficially on human health. Other than that, walnut trees are cultivated because of high-quality wood, which has application in numerous industries.

Walnut tree can reach 40 to 60 feet in height and develop a crown of the same size.

Bark of walnut tree is smooth and greenish-brown when the tree is young. It becomes grey and covered with fissures when the tree grows old.

Walnut tree has feathery leaves that consist of 5 to 9 alternately arranged leaflets.

Walnut tree has a strong and deep taproot. It produces chemicals (called juglones) which prevent growth of other plants in the close proximity to the tree.

Male flowers are arranged in dropping catkins. Female flowers are short and spiky. They are arranged in the clusters that consist of 2 to 5 individual flowers. Flowers can be cross- or self-pollinated.

Walnut tree produces a stone fruit covered with green husk. Seed kernels are protected with a brown shell.

The walnut's botanical name, Juglans, originates in Roman mythology. According to an ancient myth, Jupiter, who was also known as Jove, lived on walnuts when he lived on earth. Therefore Romans called walnuts Jovis glans, meaning 'the glans of Jupiter.' The botanical name of the English walnut, Juglans regia, means the 'royal nut of Jupiter'.

Walnut was originally grown for its nuts and was introduced by the Romans for that purpose. Later it was grown for its timber, which is fine with a decorative, wavy grain.

Walnut is known as “karyon” in Greek language, which means “head”. The name originates from the fact that walnut shell looks like a skull which protects brain-like kernel located beneath it.

Due to high amount of oils in the kernel, walnut becomes rancid after exposure to the atmospheric oxygen. The brown shell delays this effect and keeps the seed fresh and tasteful.

Walnuts are a rich source of vitamins A, E, K and vitamins of the B group and minerals such as manganese, magnesium, phosphorus and iron.

Walnuts can be consumed as snack, or as a part of various desserts and salty dishes.

Around 30 different varieties of walnuts are used in human diet.

Walnuts can improve blood flow, reduce cholesterol level, decrease inflammation and accelerate wound healing. Despite these beneficial properties, walnuts may induce strong allergic reaction in sensitive persons.

Compounds extracted from the leaves of walnut tree can improve function of liver and kidney and reduce blood sugar level.

Pigments isolated from the green husk are used for dyeing of fabrics.

The crushed leaves smell like polish.

Walnut shells are used in the production of grit paper, glues, plastics and cleaning products.

Walnut wood is used for the manufacture of flooring, furniture, musical instruments, panels, veneers and gunstocks.

Lifespan of walnut tree depends on the species. Walnut tree can survive from 50 to 250 years.

Pollinated by wind, female flowers develop into a fruit with a green, fleshy husk and a brown, wrinkled walnut.

The English walnut is susceptible to fungal diseases, as well as walnut blight, which causes small black spots on the leaflets and can lead to dieback of new shoots and damaged fruit. Walnut leaf blotch can cause leaves to fall prematurely but doesn't cause lasting damage to the tree.