The walnut is the edible seed of deciduous trees belonging to the Juglandaceae family. There exist at least thirty different cultivars of walnut. The three popular varieties grown for their commercial purpose are the English, or Persian, walnut (Juglans regia), the Black walnut (Juglans nigra), and the White, or Butternut, walnut (Juglans cinerea). The walnut tree can reach a height of twenty-five meters and, depending on the climate, may only start bearing fruit after five to ten years. In California, where most walnuts come from, harvesting starts in August.

The walnut fruit is wrapped in a green and fleshy husk. Walnut fruits are ready for harvesting when this green hull starts to crack open, exposing the light brown, hard-shelled walnut inside. The walnut kernel consists of two uneven, corrugated lobes, off-white in colour and covered by a papery thin, light brown layer. The lobes are partially attached to each other. Drying the nut is an extremely accurate process, as this is linked with shelf life.

Walnuts might be eaten plain raw from the shell, but also roasted, salted or sweetened. Crushed kernels are used to be sprinkled over salads, deserts, sundaes or pies.

The seeds contains a high source of nutrients, especially proteins. Studies show that walnuts positively affect cardiovascular diseases. Walnuts lower blood cholesterol. The walnut is very popular in the food industry, as well can be eaten as snacks.


Despite of the many different varieties, only six of these account for over eighty-five per cent of all nuts. These types are Chandler, Hartley, Howard, Tulare, Serr and Vina. 


  • Jumbo size: walnuts of which 88 percent have a diameter larger than 80/64 inches (317mm).
  • Large size: walnuts of which 88 percent have a diameter larger than 77/64 inches (305mm). 
  • Medium size: walnuts of which 12 percent have a diameter smaller than 77/64 inch (305mm) and 88 percent have a diameter larger than 73/64 inches (290mm).


Around 35% of the American walnuts are sold in shell. Between the rest, the following distinction is made:
  • Walnut halves: To qualify as halve, the nuts should be 7/8 or more intact. 85 percent of the nuts should consist of halve kernels.
  • Walnut pieces and halves: 20% or more are half kernels
  • Walnut pieces: portions of kernels cannot pass through 24/64 inch (953mm) round openings.
  • Walnut medium pieces: No less than 98 percent may pass through a 32/64 inch (127mm) screen. No more than 1 percent may pass through a 8/64 (318mm) screen.
  • Walnut small pieces: portions of kernels may pass through 24/64 inch (953mm) round openings, but not through 8/64 inch (318mm) round openings.
  • Walnut meal: fine powder.
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Proximates Units
Energy kcal 654
Protein g 15,23
Carbohydrate g 13,71
Fiber g 6,7

Total fat g 65,21
Saturated fat g 6,126
Monounsaturated fat g 8,933
Polyunsaturated fat g 47,174
Cholesterol mg 0

Calcium mg 98
Iron mg 2,91
Magnesium mg 158
Phosphorus mg 346
Potassium mg 441
Sodium mg 2
Selenium mcg 4,9

Vitamin A IU 20
Vitamin B6 mg 0,537
Vitamin C mg 1,3
Vitamin E mg 0,7
Vitamin K mcg 2,7
Carotene, beta mcg 12
Carotene, alpha mcg 0
Cryptoxanthin, beta mcg 0
Lutein + zeanxanthin mcg 9
* Walnuts are unroasted
"Source: USDA National Nutrient Database
for Standard Reference, Release 26 (2013)"
g = gram; mg = miligram ; mcg = microgram; IU = International Units


Over 98% of the total U.S. commercial crop, which is two-thirds of world's commercial walnuts, are produced in California. Other large walnut producing countries are China, Iran, Turkey, Chile, Ukraine, Moldavia and France. The walnut is also grown in the Netherlands. 


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