A walnut tree may include any member of the Juglans genus. These are deciduous trees that are native to temperate climates in the Northern hemisphere, including most of the United States. The most well-known walnut tree is the common walnut (Juglans regis), which is widely cultivated for its nuts and lumber. While all of these trees produce edible nuts, the common walnut has a large nut with a thin shell. These characteristics make the common walnut ideal for eating raw, but it is also eaten in a variety of other ways.
Black WalnutThe Black Walnut tree is most common in California and is used as an herbal remedy for gastrointestinal ailments. It has astringent properties and may also have antibiotic effects.
Walnut oilWalnut oil is expensive and, therefore, used sparingly in salad dressings and sauces, especially in French cuisine. It should be refrigerated, and can be restored to a liquid state by allowing it to warm for an hour or so.
Walnut inkWalnut ink is usually a very dark brown and was used extensively in the Middle Ages. It is colorfast and extremely resistant to solvents.
JugloseJuglose is a toxin produced by the roots of the walnut tree that causes many other plants to slowly die. Walnut chips and sawdust should not be used as a mulch for these susceptible plants.
Walnut husk flyThe walnut husk fly is a serious pest that attacks walnuts in the western United States during the later part of the growing season. It may also infest peach trees and other fruit trees that have been planted nearby.
Washington State University provides an overview of the walnut husk fly, especially in regard to its effect on walnut trees.
Walnut caterpillarThe walnut caterpillar is another common walnut tree pest that also infests other trees, such as hickory, oak and pecan.
Texas A&M University Department of Entomology provides an overview of the walnut caterpillar, including its life cycle, habitat and status as a walnut tree pest.