Black walnut Juglans nigra

The black walnut is monoecious, meaning that both male and female flowers grow on the same tree. The male flowers are long cylindrical catkins, which produce pollen in April and May. The female flowers grow at the end of shoots, and once fertilised form clusters of fruits which ripen around October to form the hard-shelled nuts.

Introduced to Europe at some point in the early 17th century, the black walnut is rare compared to the common walnut (Juglans regia). Despite producing edible nuts the black walnut is notoriously difficult to extract from its shell and requires significant preparation before it can be eaten. As a result the common walnut is the variety cultivated for eating.

However the black walnut is not without its practical uses. Like the common walnut its timber is highly valued as 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. Indeed, during the American Civil War, the phrase 'to shoulder walnut' meant to enlist as a soldier. By the time the Second World War came about its meaning had changed to indicate the starting of an aeroplane, which at the time often had propellers made of walnut.

In 1709 a harsh winter in continental Europe damaged walnut trees to such an extent that a ban was imposed on the export of timber to Britain. An alternative was sought and duly found in the USA in the shape of Juglans nigra. For some time it was the cabinet and veneer maker's wood of choice until mahogany was discovered at which point its popularity diminished somewhat.

The black walnut is so called not only for its dark timber but also for its bark which ranges from dark brown to black and has distinctive thick ridges.