Information about Black Walnut

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

The Black Walnut or American 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, northern Florida and southwest to central Texas.

It is a large deciduous tree attaining heights of 30–40 metres (100–130 feet). 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 8–10 cm long, the female flowers terminal, in clusters of two to five, ripening in the autumn into a fruit 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 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 juice will often be a yellow brown at first, then rapidly assume 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. 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

• Extensive information about black walnuts
• Flora of North America: J. nigra RangeMap:
• Juglans nigra images at bioimages.vanderbilt.edu
• Monday Garden: Black Walnut
• Harvesting Black Walnuts
• Growing Black Walnut
• Black Walnut crackers
• Selling Black Walnuts
• Black Walnut Diagnostic photos: tree, leaves, bark and fruit
• Hoadley, B. (1990). Identifying Wood: Accurate Results with Simple Tools. Taunton Press, 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
• The Hiker's Notebook

Leaf detail. Note the notch at the base of the leaflet.	Fruit.	Detail of bark.	Cross-section of a Black Walnut board. This particular board is over 140 years old, demonstrating the durability.