page_title: Juglans
section_title: Nuts and kernels
hierarchical_section_title: Juglans / Cultivation and uses / Fruit / Nuts and kernels
caption_attribution_description: English: Walnuts
context_page_description: Walnut trees are any species of tree in the plant genus Juglans, the type genus of the family Juglandaceae, the seeds of which are referred to as walnuts. All species are deciduous trees, 10–40 metres tall, with pinnate leaves 200–900 millimetres, with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts, but not the hickories in the same family.
  The 21 species in the genus range across the north temperate Old World from southeast Europe east to Japan, and more widely in the New World from southeast Canada west to California and south to Argentina. China produces half of the world total of walnuts.
context_section_description: The nut kernels of all the species are edible, but the walnuts most commonly traded are from the J. regia, the only species which has a large nut and thin shell. J. nigra kernels are also produced commercially in the US.
  Two-thirds of the world export market and 99% of US walnuts are grown in California's Central Valley and in Coastal Valleys, from Redding in the north to Bakersfield in the south.  Of the more than 30 varieties of J. regia grown there, Chandler and Hartley account for over half of total production. In California commercial production, the Hinds' black walnut (J. hindsii) and the hybrid between J. hindsii and J. regia, Juglans x paradox, are widely used as rootstocks for J. regia cultivars because of their resistance to Phytophthora and to a very limited degree, the oak root fungus.  However, trees grafted on these rootstocks often succumb to black line.
  In some countries, immature nuts in their husks are preserved in vinegar. In the UK, these are called pickled walnuts and this is one of the major uses for fresh nuts from the small scale plantings. In Armenian cuisine, unripe walnuts, including husks, are preserved in sugar syrup and eaten whole. In Italy, liqueurs called Nocino and Nocello are flavoured with walnuts, while Salsa di Noci (walnut sauce) is a pasta sauce originating from Liguria. In Georgia, walnuts are ground with other ingredients to make walnut sauce.
  Walnuts are heavily used in India. In Jammu, it is used widely as a prasad (offering) to Mother Goddess Vaisnav Devi and, generally, as a dry food in the season of festivals such as Diwali.
  The nuts are rich in oil, and are widely eaten both fresh and in cookery. Walnut oil is expensive and consequently is used sparingly; most often in salad dressings.  Walnut oil has been used in oil paint, as an effective binding medium, known for its clear, glossy consistency and nontoxicity.
  Manos and Stone studied the composition of seed oils from several species of the Rhoipteleaceae and Juglandaceae and found the nut oils were generally more unsaturated from species which grow in the temperate zones and more saturated for species which grow in the tropical zones.  In the northerly-growing section Trachycaryon, J. cinerea oil was reported to contain 15% linolenate (the report did not specify whether the linolenate was the alpha (n-3) or gamma (n-6) isomer, or perhaps a mixture), 2% of saturated palmitate, and a maximum concentration of 71% linoleate.  In the section Juglans, J. regia nut oil was found to contain from 10% to 11% linolenate, 6% to 7% palmitate, and a maximum concentration of  linoleate (62% to 68%).  In the section Cardiocaryon, the nut oils of J. ailantifolia and J. mandshurica were reported to contain (respectively) 7% and 5% of linolenate, 2% of palmitate, and maximum concentrations of 74% and 79% linoleate.  Within the section Rhysocaryon, the nut oils of the  U.S. native black walnuts J. microcarpa and J. nigra were reported to contain (respectively) 7% and 3% linolenate, 4% and 3% palmitate, and 70% and 69% linoleate.  The remaining results for black walnuts were: J. australis contained 2% linolenate, 7% palmitate, and 61% linoleate; J. boliviana contained 4% linolenate, 4% palmitate, and 70% linoleate; J. hirsuta contained 2% linolenate, 5% palmitate, and 75% linoleate; J. mollis contained 0% linolenate, 5% palmitate, 46% linoleate, and 49% oleate; J. neotropica contained 3% linolenate, 5% palmitate, and 50% linoleate; and  J. olanchana contained only a trace of linolenate, 9% palmitate, and 73% linoleate;
caption: Persian walnut (Juglans regia) seeds
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