Black walnut
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The Black Walnut (Juglans nigra L.) is a native of eastern North America, where it grows, mostly alongside rivers, from southern Ontario, Canada west to southeast South Dakota, south to Georgia and southwest to central Texas.
It is a large deciduous tree attaining heights of 30–40 metres. 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 centre, 7–10 cm long and 2–3 cm broad. The male flowers are in drooping catkins 8 to 10 cm long, the female flowers terminal, in clusters of two to five, ripening in the autumn into a fruit with a browish-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 Black Walnut was introduced into Europe in 1629. It is cultivated there as a forest tree for its high quality wood. It is more resistant to frost than the Persian Walnut, but thrives best in the warmer regions of Europe of fertile, lowland soils with a high water table. It is a light-demanding species. The wood is used to make furniture and rifle stocks, and oil is pressed from the seeds.
The Black Walnut produces a substance that is toxic or "allelopathic" to other plants called juglone. It interferes with the healthy development of other plants, especially plants in the Nightshade family (e.g. tomatoes), causing wilting and yellowing of the foliage. This has caused some to believe that nothing grows under a Black Walnut, but there are many varieties of plants that can. Fescue grass is a type of grass that is allelopathic to the Black Walnut
Use as food
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 shell itself is so strong that it is sometimes used to strengthen car tires. The shell often protrudes into the meat, so whole kernels are often not obtainable.
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.
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 (in the United States misnamed the English 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, coffins, and a variety of other woodworking products. It is so valuable that so-called "Walnut Rustlers" have been known to harvest it illegally by posing as forestry officials, cutting trees during the night, and even using helicopters to take them away quickly; such overharvesting has greatly reduced its numbers and range since colonial times.External links and references
- [Monday Garden: Black Walnut]
- [Harvesting Black Walnuts]
- [Growing Black Walnut]
- [Black Walnut crackers]
- [Black Walnut] Diagnostic photos: tree, leaves, bark and fruit
- Dirr, Dr. Michael A. Manual of Woody Landscape Plants. Stipes Publishing. ISBN 0875637957
- Petrides, George A. and Wehr, Janet. Eastern Trees. Houghton Mifflin Company. ISBN 0395904552
- [Flora of North America, Profile and map: J. nigra]
- [Juglans nigra images at bioimages.vanderbilt.edu]
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