Juglans nigra: Wikis


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Eastern Black Walnut
Leaves and fruit
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Fagales
Family: Juglandaceae
Genus: Juglans
Species: J. nigra
Binomial name
Juglans nigra

The Eastern Black walnut (Juglans nigra) is a species of flowering tree in the hickory family, Juglandaceae, that is native to eastern North America. It grows mostly in riparian zones, from southern Ontario, west to southeast South Dakota, south to Georgia, northern Florida and southwest to central Texas. Isolated wild trees in the Upper Ottawa Valley may be an isolated native population or may have derived from planted trees.

The black walnut is a large deciduous tree attaining heights of 30–40 feet (9.1–12 m). Under forest competition it develops a tall, clear bole; the open-grown form has a short bole and broad crown. The bark is grey-black and deeply furrowed. The pith of the twigs contains air spaces. The leaves are alternate, 30-60 cm long, odd-pinnate with 15-23 leaflets, the largest leaflets located in the center, 7-10 cm long and 2-3 cm broad. The male flowers are in drooping catkins 8-10 cm long, the female flowers terminal, in clusters of two to five, ripening during the autumn into a fruit (nut) with a brownish-green, semi-fleshy husk and a brown corrugated nut. The whole fruit, including the husk, falls in October; the seed is relatively small and very hard. The tree tends to crop more heavily in alternate years.

While its primary native region is the midwest and east central United States, the black walnut was introduced into Europe in 1629. It is cultivated there and in North America as a forest tree for its high quality wood. Nuts are produced more by open-grown trees. Black walnut is more resistant to frost than the Persian walnut (also known as the English walnut), but thrives best in the warmer regions of fertile, lowland soils with a high water table. It is a light-demanding species. The wood is used to make furniture, flooring, and rifle stocks, and oil is pressed from the seeds. Nuts are harvested by hand from wild trees. About 65% of the annual wild harvest comes from the U.S. state of Missouri and the largest processing plant is in Stockton, Missouri.[citation needed] The black walnut nutmeats are used as an ingredient in food while the hard black walnut shell is used commercially in abrasive cleaning, cosmetics, and oil well drilling and water filtration.

Where the range of J. nigra overlaps that of the Texas black walnut J. microcarpa, the two species sometimes interbreed, producing populations with characteristics intermediate between the two species[1]



In addition to its use as a shade tree, J. nigra can be used for the fruits it produces, and for lumber.


Black walnut nuts are shelled commercially in the United States. The nutmeats provide a robust, distinctive, natural flavor and crunch as a food ingredient. Popular uses include ice cream, baking and confection. Consumers include black walnuts in traditional treats such as cakes, cookies, fudge, and pies during the fall holiday season. The nut’s strong nutritional profile leads to uses in other foods such as salads, fish, pork, chicken, vegetables and pasta dishes.

Nutritionally similar to the milder-tasting English walnut, the black walnut kernel is high in unsaturated fat and protein. An analysis of nut oil from five named J. nigra cultivars (Ogden, Sparrow, Baugh, Carter and Thomas) showed that the most prevalent fatty acid in J. nigra oil is linoleic acid (27.80&nbsp— 33.34 g/100g dry kernel), followed (in the same units) by oleic acid (14.52&nbsp—&nbsp24.40), linolenic acid (1.61&nbsp—&nbsp3.23), palmitic acid (1.61&nbsp—&nbsp2.15), and stearic acid (1.07&nbsp—&nbsp1.69).[2] The oil from the cultivar Carter had the highest mol percent of linoleate (61.6), linolenate (5.97%), and palmitate (3.98%); the oil from the cultivar Baugh had the highest mol percent of oleate (42.7%); the oil from the cultivar Ogden has the highest mol percent of stearate (2.98%).

Tapped in spring, the tree yields a sweet sap that can be drunk or concentrated into syrup or sugar.[1]

Nut processing by hand

A woman's hands after removing the husks from 500 black walnuts.

The extraction of the kernel from the fruit of the black walnut is difficult. The thick hard shell is tightly bound by tall ridges to a thick husk. The husk is best removed when green as the nuts taste better if it is removed then.[citation needed] Rolling the nut underfoot on a hard surface such as a driveway is a common method; commercial huskers use a car tire rotating against a metal mesh. Some take a thick plywood board and drill a nut sized hole in it (from one to two inches in diameter) and smash the nut through using a hammer. The nut goes through and the husk remains behind.

While the flavor of the Juglans nigra kernel is prized, the difficulty in preparing it may account for the wider popularity and availability of the Persian walnut.


Black walnut drupes contain juglone (5-hydroxy-1,4-naphthoquinone), plumbagin (yellow quinone pigments), and tannin.[3] The brownish-black dye was used by early settlers to dye hair.[4] Extracts of the outer soft part of the drupe are still used as a natural dye for handicrafts.[5] The tannins present in walnuts act as a mordant aiding in the dyeing process;[6] [7]usable as a dark ink or wood stain.[8]


Black walnut is highly prized for its dark-colored true heartwood. It is heavy and strong, yet easily split and worked. Walnut wood has historically been used for gunstocks, furniture, flooring, paddles, coffins, and a variety of other woodworking products. Due to its value, forestry officials often are called on to track down walnut poachers; in 2004, DNA testing was used to solve one such poaching case, involving a 55 foot (16m) tree worth US $2500. Black walnut has a density per cubic meter of 660kg (41.2 lb/cubic foot)[9], which makes it lighter than oak.

Insect pests

Maggots (larva of Rhagoletis completa and Rhagoletis suavis) in the husk are common, though more a nuisance than a serious problem for amateurs, who may simply remove the affected husk as soon as infestation is noticed. The maggots develop entirely within the husk and thus the quality of the nutmeat is not affected.[10] However, infestations of Persian walnuts are undesirable because of they make the husk difficult to remove and are unsightly. Maggots can be serious for commercial walnut growers, who tend to use chemical treatments in order to avoid damage to the crop. [11] Some organic controls also exist, such as removing and disposing of infested nuts.[12]

The walnut curculio (Conotrachelus retentus) grows to 5 mm long as an adult. The adult sucks plant juices through a snout. The eggs are laid in fruits in the spring and summer. Many nuts are lost due to damage from the larvae, which burrow through the nut shell.[13]

The codling moth (Cydia pomonella) larva eats walnut kernels, as well as apple and pear seeds.[14]

Wilting tomato plant poisoned by juglone


The roots, nut husks, and leaves secrete a substance into the soil called juglone that is a respiratory inhibitor to some plants, such as this tomato that was grown too close to a black walnut tree. A number of other plants (most notably white birch) are also poisoned by juglone, and should not be planted in close proximity to a black walnut. Horses are susceptible to laminitis from exposure to black walnut wood in bedding.[15]

Big tree

The largest known living black walnut tree on Sauvie Island, Oregon.

The national champion black walnut is on a residential property in Sauvie Island, Oregon. It is 8 feet 7 inches (2.62 m) diameter at breast height and 112 feet (34 m) tall, with a crown spread of 144 feet (44 m).[16]




  • Hoadley, B. (1990). Identifying Wood: Accurate Results with Simple Tools. Taunton Press. p. 240 pages. ISBN 0-942391-04-7. 
  • Dirr, M. A. (1998). Manual of Woody Landscape Plants. Stipes Publishing. ISBN 0-87563-795-7
  • Petrides, G. A. and Wehr, J. (1998). Eastern Trees. Houghton Mifflin Company. ISBN 0-395-90455-2

External links


Up to date as of January 23, 2010

From Wikispecies

Juglans nigra


Classification System: APG II (down to family level)

Main Page
Cladus: Eukaryota
Regnum: Plantae
Cladus: Angiospermae
Cladus: Eudicots
Cladus: core eudicots
Cladus: Rosids
Cladus: Eurosids I
Ordo: Fagales
Familia: Juglandaceae
Genus: Juglans
Species: Juglans nigra


Juglans nigra L.


  • Species Plantarum 2:997. 1753
  • USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network - (GRIN) [Online Database]. [1]

Vernacular names

Česky: Ořešák černý
Dansk: Sort Valnød
Deutsch: Schwarznuss
English: Black Walnut
Français: Noyer noir
Italiano: Noce nero
Українська: Чорний горіх
Wikimedia Commons For more multimedia, look at Juglans nigra on Wikimedia Commons.

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