Juglans nigra
Juglans nigra, commonly known as black walnut or American walnut, is a tree species native to eastern North America. 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 3040 meters(100130 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, 3060 cm long, odd-pinnate with 1523 leaflets, the largest leaflets located in the centre, 710 cm long and 23 cm broad. The male flowers are in drooping catkins 810 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 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. 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 (16 m) tree worth an estimated US$2,500.