Both of our species are planted along roads and in farmyards, and it is sometimes not clear from herbarium labels whether certain specimens were collected from native trees—whether in a forest or allowed to persist in otherwise cleared sites. Records from the northern part of the state, particularly, have not been mapped unless they definitely represent trees believed not to have been planted. The English walnut, J. regia L., is sometimes planted in southern Michigan and may persist. Its leaflets are few (usually 7–9), nearly entire and glabrous. In our native species, the leaflets are more numerous, toothed, and ± pubescent, at least beneath (the rachis even more densely glandular-pubescent).
Our Juglans species have distinctive chambered pith, with air spaces between cross partitions.
1. Pith dark chocolate brown; fruit (also the nut within) ovoid-oblong; terminal leaflet present on mature leaves, not strongly reduced in size compared to the adjacent lateral leaflets.
1. Pith pale (tan to cream); fruit spherical; terminal leaflet absent or much smaller than the adjacent lateral leaflets.
All species found in Juglans
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. November 21, 2017. http://michiganflora.net/genus.aspx?id=Juglans.