Walnut, Black

Walnut, Black — 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 30–40 meters(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 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.

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.