Walnut
(This article is about the walnut tree. See also Walnut, California or Walnut, Illinois.)
The walnuts Juglans are a genus of plants in the walnut family Juglandaceae. They are deciduous trees, 10-40m tall, with pinnate leaves 20-90cm long, with 5-25 leaflets; the shoots have chambered pith, a character shared with the wingnuts (Pterocarya) but not the hickories (Carya) 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. The Latin name Juglans derives from Jovis glans, "Jupiter's nuts", the nut fit for a god; throughout recorded history the walnut has widely been regarded as the best nut of any.
The best-known member of the genus is the Persian Walnut or Common Walnut Juglans regia, native from the Balkans in southeast Europe, southwest & central Asia to the Himalaya and southwest China. This is the species which is widely cultivated for its delicious nuts. The Persian Walnut is often but incorrectly known as "English Walnut" in the United States (the species is not native to England).
The Black Walnut Juglans nigra is a common species in its native eastern North America, and is also widely cultivated elsewhere. The nuts are edible, but have a smaller kernel and an extremely tough shell, and they are not widely grown for nut production. Both this and Persian walnut are important for their attractive timber.
The nuts of all the species named above, as well as other species, are edible, but the walnuts commonly available in stores are the Persian Walnut, the only species which has a large nut and thin shell. A horticultural form selected for thin nut shells and hardiness in temperate zones is sometimes known as the 'Carpathian' walnut. The nuts are rich in oil, and are widely eaten both fresh and in cookery. Walnuts are also an excellent source of omega-3 fatty acids, and have been shown as helpful in lowering cholesterol. They need to be kept dry and refrigerated to store well; in warm conditions they become rancid in a few weeks, particularly after shelling. Walnut hulls are used as a dye source, yielding a rich yellow-brown color.
Species
- Juglans ailantifolia Carr. (J. cordiformis Maxim., J. sieboldiana Maxim.) - Japanese Walnut
- Juglans australis Griseb. (J. boliviana Dode) - Argentine Walnut
- Juglans brasiliensis Dode - Brazilian Walnut
- Juglans californica S. Wats. - California Walnut
- Juglans cinerea L. - Butternut
- Juglans hindsii (Jepson) R. E. Smith - Hinds' Walnut
- Juglans hirsuta Manning - Nuevo Leon Walnut
- Juglans jamaicensis C. DC. (J. insularis Griseb.) - West Indies Walnut
- Juglans major (Torrey) Heller (J. arizonica Dode, J. elaeopyron Dode, J. torreyi Dode) - Arizona Walnut
- Juglans major var. glabrata Manning
- Juglans mandschurica Maxim. (J. cathayensis Dode, J. formosana Hayata, J. hopeiensis Dode, J. stenocarpa Maxim.) - Manchurian Walnut or Chinese Walnut
- Juglans microcarpa Berlandier (J. rupestris Engelm.) - Texas walnut
- Juglans microcarpa var. stewartii (Johnston) Manning
- Juglans mollis Engelm. - Mexican Walnut
- Juglans neotropica Diels (J. honorei Dode) - Andean Walnut
- Juglans nigra L. - Black Walnut
- Juglans olanchana Standl. & L.O. Williams -
- Juglans peruviana Dode - Peruvian Walnut
- Juglans regia L. (J. duclouxiana Dode, J. fallax Dode, J. orientis Dode) - Persian Walnut, Common Walnut
- Juglans soratensis Manning -
- Juglans sigillata Dode - Iron Walnut
- Juglans steyermarkii Manning - Guatemalan Walnut
- Juglans venezuelensis Manning - Venezuela Walnut
Hybrids
- Juglans x bixbyi Rehd. - J. ailantifolia x J. cinerea
- Juglans x intermedia Carr. - J. nigra x J. regia
- Juglans x notha Rehd. - J. ailantifolia x J. regia
- Juglans x quadrangulata (Carr.) Rehd. - J. cinerea x J. regia
- Juglans x sinensis (D. C.) Rehd. - J. mandschurica x J. regia
