Common walnut - World Crops Database

Walnuts

The Common walnut, Juglans regia, is a deciduous tree, native to Central Asia, specifically Iran and India. This tree has been cultivated for thousands of years, making it one of the oldest known tree foods. It is grown worldwide for its edible nuts and its wood.

The primary use of the Common walnut is for its nuts, which are eaten raw or cooked. The wood from the tree is highly valued for its hardness, fine grain, and dark color, used in making furniture and veneers. Additionally, parts of the plant have been used in traditional medicine, and the husks have served as a source for natural dyes.

Names

Scientific
   Juglans regia
English
   Common walnut
   English walnut
   Persian walnut
   Walnut
Dutch
   Gewone walnoot
   Okkernoot
   Perzische walnoot
   Walnoot
Spanish
   Nogal común
   Nogal español
   Nogal europeo
French
   Noyer commun
   Noyer royal
German
   Baumnuss
   Echte Walnuss
   Persische Walnuss
   Walnuss
   Walnussbaum
Italian
   Noce bianco
   Noce da frutto

Taxonomy

Order
   Fagales
Family
   Juglandaceae
Genus
   Juglans
Species
   Juglans regia (Common walnut)

Basic information and facts

Origin:

Native to a wide region stretching from the Balkans eastward to the Himalayas and Southwest China.

Distribution:

Widely cultivated across temperate regions of the world, including Europe, Asia, and North America..

Annual, biennial, or perennial:

Perennial.

Flowers:

Male (staminate) flowers are yellowish-green catkins, hanging in clusters. Female (pistillate) flowers are small, greenish, and appear in short spikes at the tips of new growth. Both male and female flowers are borne on the same tree (monoecious).

Leaves:

Large, odd-pinnately compound leaves, typically 20-40 cm (8-16 inches) long, with 5 to 9 (sometimes up to 13) ovate leaflets. The leaves have a distinctive aromatic scent when crushed.

Fruits:

A round to oval drupe, 3-6 cm (1.2-2.4 inches) in diameter, encased in a green, fleshy husk that turns brown and splits open at maturity. Inside is the familiar hard-shelled nut, which contains the edible kernel.

Climate and weather:

Prefers temperate climates with distinct seasons. It needs a cold period for proper dormancy and nut production but is sensitive to late spring frosts which can damage new growth and flowers. Requires full sun and good air circulation.

Pollination:

Wind-pollinated. Walnut trees are monoecious, meaning they have separate male and female flowers on the same tree, but the timing of pollen release and female flower receptivity can vary, potentially requiring cross-pollination for optimal yields.

Height:

Can grow to a height of 20-35 meters (65-115 feet), with a broad, spreading crown.

Spacing:

For nut production, trees are typically spaced 9-15 meters (30-50 feet) apart to allow for their large mature size and ample sunlight.

Propagation:

Primarily propagated by grafting desirable cultivars onto rootstock, or by planting seeds (nuts) for establishing new rootstock or for genetic diversity.

Insect pests:

Susceptible to various pests including walnut husk fly, codling moth, walnut aphid, and ambrosia beetles.

Diseases:

Common diseases include bacterial blight, anthracnose, crown gall, and various cankers. Maintaining good air circulation and tree health can help prevent some issues.

Harvesting:

Nuts are harvested when the green husk dries, cracks, and the nuts fall to the ground, typically in late summer to early autumn. They are then collected, hulled (if husks haven’t fully separated), washed, and dried.

Uses:

Highly valued for its edible nuts, which are consumed fresh, roasted, or used in baking and confectionery. The timber is prized for its strength, durability, and beautiful grain, making it ideal for furniture, cabinetry, flooring, and gunstocks. Walnut leaves and husks also have traditional uses in dyes and medicinal preparations.