Coefficient of Conservatism:
Coefficient of Wetness:
B. S. Walters
Stream banks and swamps, as well as upland beech-maple, oak-hickory, and mixed hardwood stands. The Alpena and Benzie Co. records, and probably also the North Manitou Island plants, are of individuals seeding in from planted trees, and an Otsego Co. specimen is suspected of being planted and not mapped. Most, if not all, of the Upper Peninsula records, however, appear to be of native trees in forested floodplain settings. The Bois Blanc Island trees (Mackinac Co.) are native in mature upland woods.
There are some pubescence differences that will help to distinguish this species from the black walnut, even when the distinctive dark pith is not exposed. In J. cinerea, there is often a pad of dense small hairs extending transversely along the upper margin of the old leaf scars; in J. nigra, this pad is absent, although the circular area of bud pubescence is confusing, and some specimens are ambiguous. The underside of the leaflets in J. cinerea is covered with mostly stellate hairs, while in J. nigra the pubescence is sparser and mostly of simple hairs. The pubescence of J. cinerea, including that on the fruit, is stickier than that of J. nigra.
Butternuts in Michigan are being decimated by Butternut canker (Sirococcus clavigignenti-juglandacearum), a fungus that produces stem cankers that girdle and kill adult trees.
Butternut will apparently hybridize readily with the occasionally cultivated Japanese heartnut, Juglans ailanthifolia Carr., when they come into contact, producing J.×bixbyi Rehd. The hybrids can be quite difficult to distinguish from typical butternuts. If you see a vigorous, large–leaved butternut showing no apparent blight symptoms, it may be a hybrid, especially if near urban areas or farms. Herbarium specimens of the hybrids look quite like butternuts, but can be distinguished by a few subtle features. In butternut, the leaf scar is essentially flat across the top, while in hybrids there tends to be a clear notch in the middle of the upper part of the leaf scar. In addition, the lenticels of butternut are more or less round, while those of the hybrid are clearly elongated vertically. Additional features and more details are available in Farlee et al. (2009) and Ross-Davis et al. (2008). Specimens are scarce, but S. Zera has documented the hybrid from Washtenaw Co., and it may be overlooked in other areas.