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', 'Booth', 'Bear Creek' and 'Kenworthy' are among the best cultivars for Ontario.
The butternut is very susceptible to an introduced fungus disease called 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 also believed that some trees are resistant to this disease. Through breeding and continuing to plant pure butternut seedlings, identified by DNA testing, it may be possible to save this species. All of the cultivars from the Grimo Nut Nursery have been DNA tested and all are true butternut.
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 called buartnuts, the "bu" from butternut and the "eartnut" from heartnut.
'Mitchell', from Scotland, Ontario is the best and only good cracking 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.
Commercial butternut orchards are a risky venture. Only grafted cultivars should be grown because they are much better cracking than native or wild stock. Since the tree is relatively rare in the wild, the price of the nuts would be higher than any other nuts. That being said, the deadly fungus is widespread and as such may end any chances of realizing any true profits.
The grafted 'Mitchell' trees would be an exception to this, since it does show resistance to the disease, probably derived from the heartnut parent. Heartnut trees have shown a high degree of resistance to the fungus so there is a better chance of marketing buartnuts, especially in colder regions like climate zone 5, where heartnut is not successful.