Walnuts have a long and rich history. Historians think that walnuts originally grew in the ancient nation of Persia and preserved walnuts have been discovered at archaeological digs dated earlier than 2000 BC. Persians and Greeks grew walnut trees and through trading spread them to southern Europe and Asia Minor. Documentations show that ancient Greeks and Romans used both the walnut and its oil. Walnuts were thought to be sacred; ancient Romans thought they were eaten by the gods and in Persia only royalty could eat the nut. Later, walnuts served as an important food in Europe during Medieval times. Walnut oils were also used by famous European painters such as Monet and Cezanne as a medium to mix pigment.
There are about 15 different varieties of walnut, but the main types are:
English walnuts (Juglans regia) are the most common type of walnut. They actually are not grown in England but are given their name because of the English traders that introduced the walnut to early colonists. In the mid-1880s the English walnut was brought to California, and today California is the largest producer of these walnuts in the world. They are so popular because they have a relatively thin brown shell, making it easy to get the nutmeat. They have a sweet flavor that is offset by the slightly bitter skin.
Black walnuts (Juglans nigra) are named for their black shells. They are native to the western portion of the United States and are grown west of the Rockies and in California. Shelling black walnuts is a difficult process because they have a very thick shell that is hard to crack. Common ways of shelling black walnuts include using pliers, hammers, or even driving over the nuts with a car! Because of the shape of the shell it is very difficult to remove the nutmeat in one piece. On top of that, the walnut oils that are often produced when cracking the shell can stain hands and clothing. Black walnuts have a much stronger, often disagreeable flavor than English walnuts. They are not normally eaten alone but instead are mixed into savory dishes.
yclept informs me that Black walnut trees are an endangered species and that it is illegal to cut one down
The white walnut (Juglans cinerea) or butternut is grown in roughly the same regions as black walnuts. This type of walnut is very common and white walnuts are generally not sold for eating. Butternut extracts were used by early American settlers to dye clothing, including the uniforms of Confederate soldiers during the American Civil War. Because of this the word "butternut" is also a slang term for a Confederate soldier.
The walnut plant is related to the pecan and hickory family. Walnut trees grown to about 100 feet tall and produce nuts every year in the fall. The walnut is encased in a thick, textured shell that is surrounded by a husk like pecans. The brown or black shell is about 2 inches in diameter and has a characteristic wrinkled texture. Walnuts are harvested around September by shaking the trees to dislodge ripe nuts. Walnut trees are also grown for their wood. The wood from black walnut trees is particularly hard and durable and is often used to make furniture. It has a deep brown to purplish finish. White walnut wood is lighter in color and softer than black walnut wood. It is also used in furniture and can be used for carving.
Walnuts are often added to baked goods such as cookies, cakes, and brownies. They are a main ingredient in a variety of Middle Eastern desserts such as one of my favorites, baklava. Walnuts also blend nicely with savory foods such as grains and stuffings and they are often added to pestos. Walnut oil extracted from the nut can also be purchased. It has a nice nutty flavor and is generally drizzled over cooked vegetables and salads.
Walnuts are a good source of protein, vitamin B, folic acid, and vitamin E. They also have an extremely high level of polyunsaturated fat and are a good source of omega-3 fatty acids.
http://www.mycustompak.com/healthNotes/Food_Guide/Walnuts.htm
http://www.pathcom.com/~wgbz/walnut.htm
http://homecooking.about.com/library/weekly/aa060198.htm
http://www.smokymountainnews.com/issues/03_03/03_05_03/mtn_voices.html
http://www.vegparadise.com/highestperch411.html