Two types of walnuts are grown and eaten around the world: the English walnut (which is also known as the Persian walnut) and the black walnut. Most of the walnuts you find at your local grocery store are the English ones, which have a thinner shell and a larger nut. Black walnuts have tough shells and don't taste as good as English walnuts.
Black walnuts grow throughout the eastern United States, but English walnuts favor a more mild environment. Early settlers in America tried to grow English walnuts in Pennsylvania and Massachusetts, but the walnuts floundered. However, when the nuts were planted in the more temperate areas of California, they flourished. According to the Food and Agriculture Organization of the United Nations, the United States produces 20 percent of the world's walnuts (primarily English walnuts). China grows the most, followed by the United States, Iran, Turkey, Ukraine, and Romania.
Walnuts are harvested in the fall. When the nuts are ripe, the outer hull, or husk, splits open and the walnut falls to the ground. To get the more reluctant walnuts, growers use mechanical shakers to wiggle the nuts loose. The walnuts are then allowed to dry before they are shelled and processed.
When people think of nuts, they very often think of peanuts first. Learn about this nut in the next section.