The black walnut is a large deciduous tree attaining heights of 30–40 meters. 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 black walnut was introduced into Europe in 1629. It is cultivated there and in North America as a forest tree for its high quality wood.