Walnut vs. Hickory Nut

Walnuts

• Most walnuts of the type used for baking, shelling and eating out of hand are from the English, or Persian, walnut tree (Juglans regia). Although planted widely across the United States, it reliably bears nuts only in areas with long warm seasons. It is hardy from U.S. Department of Agriculture (USDA) zone 4 through 9. The more common black walnut (Juglans nigra), a native species widespread across the eastern United States, is hardy from USDA zones 5 through 9a.

Juglone Toxicity

• Black walnuts produce a compound called juglone that causes many kinds of nearby plants to wilt and slowly decline. English walnuts and hickories also produce juglone but in smaller concentrations. All parts of the black walnut contain juglone, with the highest concentrations occurring in the tree’s buds, roots and nut hulls. Juglone is carried to the ground and to plants below by water dripping from upper branches. So sensitive plants should not be located directly beneath a black walnut. Some plants tolerate juglone exposure. They include winter daphne (Daphne odora), hardy from USDA zones 7 through 9, and most species of viburnum (Viburnum spp.), hardy from USDA zones 2 through 10, depending on the species.

Hickory Species

• The dozen or so species of hickory in the eastern one-half of the United States have been important to local people and economies for a long time; they are used for food, fuel and woodworking. Most people probably are familiar with the pecan tree (Carya illinoensis), which produces the largest nuts of any hickory and is hardy in USDA zones 5b through 9a. Shagbark hickory (Carya ovata) is among the most distinctive in the forest, named for the long strips of exfoliating bark covering its trunk and large branches; it is hardy from USDA zones 5 through 8a. Two other common species are mockernut hickory (Carya tomentosa), hardy from USDA zones 4 through 9, and the pignut (Carya glabra), hardy from USDA zones 5 through 9.

Nut Edibility

• Omitting the pecan and English walnut, which are produced on an agricultural level, both the black walnut and several kinds of hickories have edible nuts. The black walnut's nut has a stronger, muskier flavor than the English walnut's nut and may be an acquired taste, though it is considered an interesting addition to baked goods and other cooking. Of the hickories, the mockernut hickory produces the largest nutmeats in relation to the size of its shell, followed by the shagbark hickory and shellbark hickory (Carya laciniosa), which is hardy from USDA zones 5 through 8. All the nuts feature a thick, green outer husk, which must be removed prior to shelling the nut meats. Black walnuts, in particular, become stained and infused with a bitter flavor if shelled after the husk begins to blacken.