The native butternut, also known as white walnut, is the hardiest member of the walnut family. It is found throughout Southern Ontario and is often found growing in association with black walnut. Though it has similar timber qualities to the black walnut, it is prized also as a carving wood.
When the green husk is removed, it reveals an oval dark brown shell with deep longitudinal ridges. The kernel is often caught in the shell cavities making the meat difficult to remove. Grafted cultivars have been selected for cracking quality. Our best selections will usually come out in 2 pieces when cracked from end to end with a hammer or a suitable nut cracker. Beckwith, George Elmer, and Kenworthy are among the best cultivars for Ontario.
The butternut is very susceptible to the fungus disease Sirococcus claviginenti-juglandacearum, that causes cankers and open oozing wounds in the trunk, eventually killing the tree. It is estimated that over 90% of the trees in North America are infected. It is believed that the disease was introduced from offshore. The tree has been placed on the endangered list. It is believed that some trees are resistant to this disease. Through breeding it may be possible to save this species.
The butternut leafs out and blooms about the same time as heartnut, Persian walnut and Manchurian walnut. As a result it crosses readily with them. Along with hybrid vigor, low fertility and disease resistance, the crosses often exhibit the hardiness of the butternut and unfortunately the thick shell and poor cracking quality of the parents. Very few good hybrids have been identified. Only heartnut so far has made a noteworthy cross. They are termed buartnuts, the “bu” from butternut and the “eartnut” from heartnut. Mitchell, from Scotland, Ontario is the best buartnut found to date. It is a productive tree having a nut shaped like a heartnut with the rough shell and hardiness of the butternut. This area in breeding has largely been neglected. It should be possible to extend the range of the heartnut through breeding with the butternut and existing buartnuts like the Mitchell.