Walnut

The walnut is the edible seed of trees in the genus Juglans, especially the Persian or English walnut (Juglans regia), which is widely cultivated in temperate regions. What we commonly call a walnut is not a true botanical nut: its outer green husk surrounds a hard shell, and the part we eat is the seed inside. The kernel is divided into two lobes separated by thin partitions and has a distinctive, wrinkled shape.

Walnuts are rich in unsaturated fats, including alpha-linolenic acid (ALA), an omega-3 fatty acid found in plants. They also provide protein, dietary fiber, minerals such as copper and manganese, and various plant compounds. Their composition can vary with variety, growing conditions and processing, so nutrition values are not identical for every walnut.

Walnuts have been cultivated for thousands of years and have a long history in Central Asia and the regions around the Caspian Sea. Today, Juglans regia is grown in many countries with suitable climates, while other walnut species are also cultivated or used locally. The trees are deciduous and can become large and long-lived. Their fruits develop during the growing season; as they mature, the green outer husk darkens and eventually splits, revealing the hard shell.

After harvest, walnuts are usually dried to reduce moisture and improve storage. They can be eaten on their own or added to breads, pastries, salads and other dishes. Because walnuts contain a high proportion of fat, they can become rancid if stored poorly, so keeping them in a cool, dry place—and, especially for shelled kernels, in an airtight container—helps preserve their quality.