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Black walnut

The strong, heavy heartwood of black walnut was historically used to make parts for guns. During the American Civil War, 'to shoulder walnut' came to mean enlisting as a soldier.

Black walnut (<em>Juglans nigra</em>)

About Kew's black walnut trees

You can visit Juglans nigra in many guises here at Kew. View other specimens planted with walnut relatives near the Rhizotron and Xstrata Treetop Walkway or drop in to the Plants and People exhibition at Museum No 1 to see artefacts made from this plant, including nutshell whistles.

Take a closer look

  • Not only is the wood of the black walnut dark, so is its bark, which ranges from dark brown to black and has distinctive thick ridges.
  • The leaves of this tree give off a pleasant aroma if rubbed.
  • Like common walnut, this tree has long leaves with leaflets arranged around a central stalk. On the black walnut however, the single leaf on the end (the terminal leaf) is usually missing.

Tree biology

The black walnut can grow to 40 metres in height although in Britain it rarely tops 30 m. It grows faster than the common walnut and has a wide head and tall, straight trunk.

Both male and female flowers grow on the same tree. The male flowers are long cylindrical catkins; the female flowers grow at the end of shoots.

The roots, nut husks, and leaves secrete a substance into the soil called juglone that inhibits the growth of other plants. This helps the walnut grow free of competition.

Cultivation and uses

The black walnut is notoriously hard to extract from its shell, but this tree is grown commercially in North America where its nuts are a popular ingredient in ice cream, cakes and sweets.

The timber is highly valued because it is heavy and strong, but easily splits without splintering. The dark heartwood has historically been used for furniture, coffins and in the manufacture of guns.

A brownish-black dye derived from the nuts was used by early settlers to dye hair.

Quick facts

  • Scientific name: Juglans nigra
  • Family: Juglandaceae
  • Place of origin: eastern and central USA
  • Conservation status: not evaluated
  • Date planted: unknown
  • Height: not recorded