The Asian walnuts produce jumbo leaflets of variable size within the leaf and hanging chains of often pointed nut cases. Black walnut produces more or less evenly sized smaller leaflets and close bunches of cannon ball like fruits. In this area the Asian species are usually seen as huge vases forking low down whereas black walnut normally produces a long single trunk, grows quite tall. Butternut is intermediate between these two in growth and foliage, tending to have a definite single trunk below the main canopy with leaves of a somewhat lesser order of size but still clearly of the same ilk (as are the fruits) of the Asian walnuts.
Asian walnuts (Japanese. Chinese) and Butternut have downy leaves, Black Walnut only sparsely hairy (can look hairless by comparison).
And the walnuts discussed here so far aren't the full extent of what is seen in this region, by any means. http://www.arthurleej.com/p-o-m-Oct14.html
