The black walnut tree is native to eastern North America. It can be found as far west as South Dakota and as far south as Texas. Male flowers, known as catkins, droop from the previous year's twig growth; smaller female flowers grow on the current season's stem. The fruit generally falls in October. In 1629, the North American black walnut was introduced in Europe, and in both North America and Europe, it is cultivated for its high-quality wood. It is used to make furniture, flooring, and rifle stocks; oil can be procured from its seeds. The black walnut flesh is used in baking, and its shell is in such diverse industries as cosmetics, oil well drilling, and water filtration.