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 "alleopathic" to other plants called juglone. It interferes with the healthy development of other plants (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 alleopathic 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 extrudes a dark, staining juice. Before eating or storage, the nuts should be cured for at least two weeks. Finally, before cracking, the unshelled nuts should be soaked in hot water for 24 hours in order to soften the shells. 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).

External link

• Monday Garden: Black Walnut
• Harvesting Black Walnuts
• Growing Black Walnut