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Black Walnut
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Black walnut or American 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.
The black walnut is a large deciduous tree attaining heights of . Under forest competition it develops a tall, clear bole; the open-grown form has a short bole and broad crown.
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Black walnut or American 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.
The black walnut is a large deciduous tree attaining heights of . 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. 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.
Use as food
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 is high in unsaturated fat and protein and has no cholesterol.
Processing by hand
The extraction of the kernel from the fruit of the black walnut is difficult. The shell is covered by a thick husk that exudes a dark, staining, strong-smelling juice. The juice will often be a yellow-brown at first, and then rapidly assumes a deep black-green color upon exposure to the air. The shell often protrudes into the meat so that whole kernels often cannot be obtained.
The husk is best removed when green as the nuts taste better if it is removed then. 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. To keep the husk juices from splattering, a board or canvas scrap may be used to cover the nut before hammering. The black walnut’s husks are known to leave durable, hard to remove stains on hands and clothing.
Before eating or storage, the nuts should be cured in a dry place for at least two weeks. Before cracking, the unshelled nuts may be soaked in hot water for 24 hours in order to soften the shells, but with a proper cracker this is not necessary. While the flavor is prized, the difficulty in preparing the black walnut may account for the wider popularity and availability of the Persian walnut.
Wood
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), which makes it lighter than oak.
Dyes and other uses
Black walnut drupes contain juglone (5-hydroxy-1,4-naphthoquinone), plumbagin (yellow quinone pigments), and tannin.
The brownish-black dye was used by early settlers to dye hair. Extracts of the outer soft part of the drupe are still used as a natural dye for handicrafts.
The tannins present in walnuts act as a mordant aiding in the dyeing process;
usable as a dark ink or wood stain.
Walnut Husk Fly
Maggots 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. Maggots can, however, be serious for commercial walnut growers, who tend to use chemical treatments in order to avoid damage to the crop. Some organic controls exist also.
Toxicity
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.
Big tree
The national champion black walnut is on a residential property in Sauvie Island, Oregon. It is 8 feet 7 inches in diameter at breast height and 112 feet tall, with a crown spread of 144 feet.
Gallery
External links
- University of Missouri Center for Agroforestry
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