J. nigra L. is the Eastern Black Walnut, prized for its high quality wood more than its nuts. Most of the crop is harvested from wild trees located in the south-central and southeastern US, although some selections have been made. Section Trachycaryon - J. cineria L., the Butternut is the only species. Native to the eastern US, this species has the most northern distribution of North American Juglans . Butternuts are used in New England to make maple-butternut candy, which is sold at the roadside on a very limited scale.
Nuts have very thick shells, and kernels are small and tend to shatter when cracked.
At least 25 cultivars have been selected, mostly for ease of cracking. Section Cardiocaryon - J. ailantifolia var. A successful breeding program has greatly changed the way walnuts are grown in California. Older cultivars bear fruit only on terminals of branches, therefore any pruning reduces yield, and trees become very large. Newer cultivars stemming from Payne' bear a large proportion of fruit from lateral buds, and thus lend themselves to hedgerow planting, and mechanical pruning.