Juglans cinerea L.
Common Name: BUTTERNUT
Coefficient of Conservatism: 5
Coefficient of Wetness: 3
Wetness Index: FACU
Physiognomy: Nt Tree

Juglans cinerea 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. At least some, if not all, of the Upper Peninsula records, however, appear to be of native trees in floodplain settings.

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 Jbixbyi 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. Specimens are scarce, but S. Zera has documented the hybrid from Washtenaw Co., and it may be overlooked in other areas.

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).

Locations

Allegan County
Alpena County
Arenac County
Barry County
Benzie County
Berrien County
Branch County
Cass County
Chippewa County
Clinton County
Delta County
Eaton County
Gratiot County
Hillsdale County
Ingham County
Isabella County
Jackson County
Kalamazoo County
Kent County
Lapeer County
Leelanau County
    Only on Manitou Islands
Lenawee County
Mackinac County
    Only on Bois Blanc, Mackinac, Round Islands
Macomb County
Mason County
Menominee County
Midland County
Monroe County
Montcalm County
Muskegon County
Newaygo County
Oakland County
Ottawa County
Saginaw County
Sanilac County
St. Clair County
St. Joseph County
Tuscola County
Van Buren County
Washtenaw County
Wayne County

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. April 6, 2020. https://michiganflora.net/species.aspx?id=1495.